TW201711959A - Graphene dispersion, process for producing same, process for producing particles of graphene/active material composite, and process for producing electrode paste - Google Patents

Graphene dispersion, process for producing same, process for producing particles of graphene/active material composite, and process for producing electrode paste Download PDF

Info

Publication number
TW201711959A
TW201711959A TW105129665A TW105129665A TW201711959A TW 201711959 A TW201711959 A TW 201711959A TW 105129665 A TW105129665 A TW 105129665A TW 105129665 A TW105129665 A TW 105129665A TW 201711959 A TW201711959 A TW 201711959A
Authority
TW
Taiwan
Prior art keywords
graphene
dispersion
mass
producing
ratio
Prior art date
Application number
TW105129665A
Other languages
Chinese (zh)
Other versions
TWI694054B (en
Inventor
Koichiro Manabe
Eiichiro Tamaki
Manabu Kawasaki
Original Assignee
Toray Industries
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Family has litigation
First worldwide family litigation filed litigation Critical https://patents.darts-ip.com/?family=58289187&utm_source=***_patent&utm_medium=platform_link&utm_campaign=public_patent_search&patent=TW201711959(A) "Global patent litigation dataset” by Darts-ip is licensed under a Creative Commons Attribution 4.0 International License.
Application filed by Toray Industries filed Critical Toray Industries
Publication of TW201711959A publication Critical patent/TW201711959A/en
Application granted granted Critical
Publication of TWI694054B publication Critical patent/TWI694054B/en

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/182—Graphene
    • C01B32/194—After-treatment
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/32—Carbon-based
    • H01G11/38—Carbon pastes or blends; Binders or additives therein
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
    • B01J13/0004—Preparation of sols
    • B01J13/0026—Preparation of sols containing a liquid organic phase
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/24—Electrodes characterised by structural features of the materials making up or comprised in the electrodes, e.g. form, surface area or porosity; characterised by the structural features of powders or particles used therefor
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/32—Carbon-based
    • H01G11/36—Nanostructures, e.g. nanofibres, nanotubes or fullerenes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2204/00—Structure or properties of graphene
    • C01B2204/20—Graphene characterized by its properties
    • C01B2204/22—Electronic properties
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2204/00—Structure or properties of graphene
    • C01B2204/20—Graphene characterized by its properties
    • C01B2204/32—Size or surface area
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
    • C01P2002/85—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70 by XPS, EDX or EDAX data
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/12—Surface area
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/22—Rheological behaviour as dispersion, e.g. viscosity, sedimentation stability
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The purpose of the present invention is to provide graphene in a form that renders the graphene highly dispersible and enables the graphene to retain high electroconductivity and ionic conductivity when used as a raw material for producing electrode materials. The present invention is a graphene dispersion which includes graphene dispersed in a solvent including 50 mass% or more N-methylpyrrolidone. When this graphene dispersion is diluted with N-methylpyrrolidone to a graphene content by weight of 0.000013, the dilution has a weight absorptivity coefficient, as measured at a wavelength of 270 nm and calculated using the following equation (1), of 25,000-200,000 cm-1. Weight absorptivity coefficient (cm-1) = absorbance/{0.000013 x (optical path length (cm) of cell)}...(1).

Description

石墨烯分散液及其製造方法、石墨烯-活性物質複合體粒子的製造方法以及電極糊的製造方法Graphene dispersion liquid, method for producing the same, method for producing graphene-active material composite particles, and method for producing electrode paste

本發明是有關於一種石墨烯分散液及其製造方法、及使用其的石墨烯-活性物質複合體粒子以及電極糊的製造方法。The present invention relates to a graphene dispersion liquid, a method for producing the same, and a method for producing a graphene-active material composite particle and an electrode paste using the same.

石墨烯是包含碳原子的二維結晶且為自2004年發現以來一直受到格外關注的素材。石墨烯具有優異的電氣特性、熱特性、光學特性及機械特性，而期待於電池材料、能量貯存材料、電子元件、複合材料等領域中廣泛應用。Graphene is a two-dimensional crystal containing carbon atoms and has been receiving much attention since its discovery in 2004. Graphene has excellent electrical, thermal, optical and mechanical properties and is expected to be widely used in battery materials, energy storage materials, electronic components, composite materials and the like.

作為石墨烯的製造法，可列舉機械剝離法、化學氣相沈積（Chemical Vapor Deposition，CVD）法、晶體外延生長（Crystal Epitaxial Growth，CEG）法等。其中，就可大量生產的方面而言，期望作為產業製造法的氧化還原法、即於利用天然石墨的氧化處理獲得氧化石墨或石墨氧化物（graphite oxide）後藉由還原反應而製造石墨烯的方法。Examples of the method for producing graphene include a mechanical peeling method, a chemical vapor deposition (CVD) method, and a crystal epitaxial growth (CEG) method. Among them, in terms of mass production, it is desirable to produce graphene by a redox method of an industrial manufacturing method, that is, after obtaining graphite oxide or graphite oxide by oxidation treatment of natural graphite, by reduction reaction. method.

於專利文獻1中，對石墨氧化物進行加熱還原，同時使其膨脹剝離，藉此製作比表面積高的薄片型石墨。In Patent Document 1, the graphite oxide is heated and reduced while being expanded and peeled off, whereby flaky graphite having a high specific surface area is produced.

於專利文獻2中，於兒茶酚的存在下對石墨烯進行化學還原並進行凍結乾燥，藉此製作分散性高的石墨烯粉末。In Patent Document 2, graphene is chemically reduced in the presence of catechol and freeze-dried to prepare a graphene powder having high dispersibility.

於專利文獻3中，於具有9,9-雙(取代芳基)茀骨架的水溶性化合物的存在下對氧化石墨烯進行化學還原，將有機溶劑與所獲得的石墨烯水分散體加以混合，然後於利用離心沈降回收的石墨烯中進而添加有機溶劑而製備石墨烯分散液。In Patent Document 3, the graphene oxide is chemically reduced in the presence of a water-soluble compound having a 9,9-bis(substituted aryl)fluorene skeleton, and the organic solvent is mixed with the obtained aqueous graphene dispersion. Then, a graphene dispersion liquid is prepared by further adding an organic solvent to the graphene recovered by centrifugal sedimentation.

於非專利文獻1中，報告有藉由使氧化石墨薄膜的肼還原反應長時間化而促進酸性基的還原，且270 nm的吸光度增大。 [現有技術文獻] [專利文獻]In Non-Patent Document 1, it is reported that the reduction of the acidic group is promoted by prolonging the ruthenium reduction reaction of the graphite oxide film, and the absorbance at 270 nm is increased. [Prior Art Document] [Patent Literature]

[專利文獻1]國際公開第2007/047084號 [專利文獻2]國際公開第2013/181994號 [專利文獻3]日本專利特開2015-059079號公報 [非專利文獻][Patent Document 1] International Publication No. 2007/047084 [Patent Document 2] International Publication No. 2013/181994 [Patent Document 3] Japanese Patent Laid-Open Publication No. 2015-059079 [Non-Patent Document]

非專利文獻1：松雄吉晃，Carbon，2010，No.245,200-205Non-Patent Document 1: Matsuo Yoshihiro, Carbon, 2010, No. 245, 200-205

[發明所欲解決之課題][Problems to be solved by the invention]

為了使石墨烯作為導電劑而有效地發揮功能，必須薄、且具有高分散性。然而，如專利文獻1般的藉由加熱膨脹還原法而製作的石墨烯的比表面積變得過大而引發凝集，分散性變差。In order for the graphene to function effectively as a conductive agent, it is required to be thin and highly dispersible. However, the specific surface area of graphene produced by the heat expansion reduction method as in Patent Document 1 is excessively large to cause aggregation, and the dispersibility is deteriorated.

即便如專利文獻2般使用分散劑，亦有因之後的凍結乾燥引起石墨烯彼此的聚集（積層凝集）而石墨烯粉末的剝離狀態變得不充分的傾向。In the case where the dispersing agent is used as in the case of the patent document 2, the graphene is aggregated (layered and aggregated) by the subsequent freeze-drying, and the peeling state of the graphene powder tends to be insufficient.

另外，於專利文獻3的手法中，具有9,9-雙(取代芳基)茀骨架的水溶性化合物於分散液製備步驟中經去除，因此石墨烯的凝集抑制效果不充分，無法防止分散液中的石墨烯的凝集。Further, in the method of Patent Document 3, the water-soluble compound having a 9,9-bis(substituted aryl)fluorene skeleton is removed in the dispersion preparation step, so that the aggregation inhibition effect of graphene is insufficient, and the dispersion cannot be prevented. Aggregation of graphene.

於如非專利文獻1般減少氧化石墨上的酸性基且修復共軛系的情況下，由酸性基減少引起的親溶劑性不充分而導致溶劑中的分散性下降，仍無法防止凝集。When the acidic group on the graphite oxide is reduced and the conjugated system is repaired as in Non-Patent Document 1, the solvophilicity due to the decrease in the acidic group is insufficient, and the dispersibility in the solvent is lowered, and aggregation cannot be prevented.

如此，石墨烯非常容易凝集，於利用氧化還原法進行製造的情況下，無法獲得充分的分散性，因此無法發揮其潛力。本發明的課題在於提供一種為高分散性、且於用於電極材料的製造原料時可維持高導電性與離子傳導性的形態的石墨烯。 [解決課題之手段]As described above, graphene is very likely to aggregate, and when it is produced by the redox method, sufficient dispersibility cannot be obtained, and thus its potential cannot be exhibited. An object of the present invention is to provide a graphene which is highly dispersible and can maintain a high conductivity and ion conductivity when used as a raw material for producing an electrode material. [Means for solving the problem]

用以解決所述課題的本發明是一種石墨烯分散液，其為石墨烯分散於含有50質量%以上的N-甲基吡咯啶酮的溶劑中而成的分散液，且利用N-甲基吡咯啶酮將石墨烯重量分率製備為0.000013而得的稀釋液的、波長270 nm下的使用下述式（1）算出的重量吸光係數為25000 cm-1 以上且200000 cm-1 以下， 重量吸光係數（cm-1 ）=吸光度/{（0.000013×比色皿的光學長度（cm））} ···（1）。The present invention for solving the above problems is a graphene dispersion liquid in which a graphene is dispersed in a solvent containing 50% by mass or more of N-methylpyrrolidone, and N-methyl group is used. Pyrrolidone having a weight fraction of graphene of 0.000013 and having a weight absorption coefficient calculated by the following formula (1) at a wavelength of 270 nm of 25,000 cm -1 or more and 200,000 cm -1 or less, weight Absorbance coefficient (cm -1 ) = absorbance / {(0.000013 × optical length (cm) of cuvette)} · (1).

另外，本發明的石墨烯分散液的製造方法為如下石墨烯分散液的製造方法，其包括： 還原步驟，包括對含有水的分散媒中所分散的氧化石墨烯進行還原； N-甲基吡咯啶酮（N-Methy Pyrrolidone，NMP）混合步驟，包括將還原步驟中所獲得的中間體分散液與含有50質量%以上的N-甲基吡咯啶酮的溶劑（含NMP的溶劑）加以混合； 強力攪拌步驟，包括以剪切速度為每秒5000～每秒50000對NMP混合步驟中所獲得的中間體分散液進行攪拌； 水分去除步驟，包括藉由將含NMP的溶劑添加與吸引過濾加以組合的手法或者蒸餾而自中間體分散液中去除至少一部分水分。 [發明的效果]Further, the method for producing a graphene dispersion of the present invention is a method for producing a graphene dispersion, comprising: a reduction step comprising: reducing a graphene oxide dispersed in a dispersion medium containing water; N-methylpyrrole a mixing step of N-Methy Pyrrolidone (NMP), comprising mixing the intermediate dispersion obtained in the reduction step with a solvent (NMP-containing solvent) containing 50% by mass or more of N-methylpyrrolidone; a vigorous stirring step comprising stirring the intermediate dispersion obtained in the NMP mixing step at a shear rate of 5000 to 50,000 per second; the moisture removal step comprising combining by adding NMP-containing solvent and suction filtration At least a portion of the water is removed from the intermediate dispersion by distillation or distillation. [Effects of the Invention]

本發明的石墨烯分散液為了作為導電助劑發揮功能而使充分薄的石墨烯充分分散存在於含有50質量%以上的N-甲基吡咯啶酮的溶劑中而抑制凝集。藉由使用所述石墨烯分散液，石墨烯於樹脂或電極糊中的分散性變得良好，且石墨烯於活性物質等無機粒子表面的吸附亦變得容易。因此，藉由石墨烯吸附於鋰離子電池等活性物質表面，可於電極中長期間地維持活性物質表面的高電子傳導性、離子傳導性。In order to function as a conductive auxiliary agent, the graphene dispersion liquid of the present invention is sufficiently dispersed in a solvent containing 50% by mass or more of N-methylpyrrolidone to suppress aggregation. By using the graphene dispersion liquid, the dispersibility of graphene in the resin or the electrode paste becomes good, and the adsorption of graphene on the surface of the inorganic particles such as the active material is also facilitated. Therefore, by adsorbing graphene on the surface of an active material such as a lithium ion battery, high electron conductivity and ion conductivity on the surface of the active material can be maintained for a long period of time in the electrode.

＜石墨烯分散液＞ 本發明的石墨烯分散液為石墨烯分散於含有50質量%以上的N-甲基吡咯啶酮（NMP）的溶劑中而成的分散液。石墨烯為單層石墨烯積層而成的結構體，且為具有薄片狀的形態者。<Graphene Dispersion Liquid> The graphene dispersion liquid of the present invention is a dispersion liquid in which graphene is dispersed in a solvent containing 50% by mass or more of N-methylpyrrolidone (NMP). Graphene is a structure in which a single layer of graphene is laminated, and has a flaky shape.

關於本發明的石墨烯分散液，使用NMP將以稀釋後的稀釋液整體設為1時的石墨烯重量分率調整為0.000013，從而獲得稀釋液，使用下述式（1）而算出的所述稀釋液於波長270 nm下的重量吸光係數（以下，僅稱為「重量吸光係數」）的值為25000 cm-1 以上且200000 cm-1 以下， 重量吸光係數（cm-1 ）=吸光度/{（0.000013×比色皿的光學長度（cm））} ···（1）。In the graphene dispersion liquid of the present invention, the graphene weight fraction when the entire diluted diluent solution is set to 1 is adjusted to 0.000013 using NMP to obtain a diluent, and the above-described formula (1) is used. The weight absorption coefficient of the diluent at a wavelength of 270 nm (hereinafter, simply referred to as "weight absorption coefficient") is 25000 cm -1 or more and 200,000 cm -1 or less, and the weight absorption coefficient (cm -1 ) = absorbance / { (0.000013 × optical length (cm) of cuvette)} · (1).

石墨烯的每單位重量的吸光度因石墨烯的剝離度而變化，單層石墨烯最高，因層數的增加或凝集的形成而變低。The absorbance per unit weight of graphene varies depending on the degree of peeling of graphene, and the single layer graphene is the highest, and becomes low due to an increase in the number of layers or formation of agglomeration.

於重量吸光係數未滿25000 cm-1 的情況下，所含有的石墨烯的剝離度或對NMP的分散性低，無法形成並維持樹脂或電極糊中的良好的導電路徑。另外，於重量吸光係數大於200000 cm-1 的情況下，由石墨烯的表面積增大引起高黏度化，因此石墨烯分散液的操作性下降。重量吸光係數較佳為40000 cm-1 以上且150000 cm-1 以下，更佳為45000 cm-1 以上且100000 cm-1 以下。When the weight absorption coefficient is less than 25000 cm -1 , the degree of peeling of the graphene contained or the dispersibility to NMP is low, and a good conductive path in the resin or the electrode paste cannot be formed and maintained. Further, when the weight absorption coefficient is more than 200,000 cm -1 , the surface area of the graphene is increased to cause high viscosity, and thus the workability of the graphene dispersion is lowered. The weight absorption coefficient is preferably 40,000 cm -1 or more and 150,000 cm -1 or less, more preferably 45,000 cm -1 or more and 100,000 cm -1 or less.

另外，以如上所述的方式製備的稀釋液的波長270 nm與600 nm下的、使用下述式（2）而算出的吸光度比（以下，僅稱為「吸光度比」）的值較佳為1.70以上且4.00以下，更佳為1.80以上且3.00以下，進而佳為1.90以上且2.50以下， 吸光度比=吸光度（270 nm）/吸光度（600 nm） ···（2）。Further, the value of the absorbance ratio calculated by the following formula (2) at a wavelength of 270 nm and 600 nm prepared as described above (hereinafter, simply referred to as "absorbance ratio") is preferably 1.70 or more and 4.00 or less, more preferably 1.80 or more and 3.00 or less, further preferably 1.90 or more and 2.50 or less, and absorbance ratio = absorbance (270 nm) / absorbance (600 nm) · (2).

吸光度中含有光的吸收成分與散射成分，散射成分因石墨烯的表面狀態而增減。於波長270 nm下，散射成分於吸光度中所佔的比例小，但於波長600 nm下，吸收成分小，因此散射成分於吸光度中所佔的比例大。於所含有的石墨烯中含有大量凝集的情況下，吸光度比未滿1.70，有於樹脂或電極糊中的良好的導電路徑的形成、維持變得困難的傾向。另外，於將石墨烯過度微粒化的情況下，吸光度比大於4.00，有變得容易於樹脂或電極糊中凝集的傾向。此處，由石墨烯分散液而調整的稀釋液的吸光度可藉由紫外可見分光光度計進行測定。所述式（1）及式（2）中的石墨烯的吸光度可藉由從由石墨烯分散液而調整的稀釋液的吸光度減去稀釋液的溶劑的吸光度來求出。The absorbance contains an absorption component and a scattering component of light, and the scattering component increases or decreases due to the surface state of the graphene. At a wavelength of 270 nm, the proportion of the scattering component in the absorbance is small, but at a wavelength of 600 nm, the absorption component is small, so the proportion of the scattering component in the absorbance is large. When a large amount of agglomerates are contained in the graphene contained, the absorbance is less than 1.70, and formation and maintenance of a good conductive path in the resin or the electrode paste tend to be difficult. Further, when the graphene is excessively atomized, the absorbance ratio is more than 4.00, and it tends to be easily aggregated in the resin or the electrode paste. Here, the absorbance of the diluent adjusted by the graphene dispersion can be measured by an ultraviolet-visible spectrophotometer. The absorbance of the graphene in the formulas (1) and (2) can be determined by subtracting the absorbance of the solvent of the diluent from the absorbance of the diluent adjusted by the graphene dispersion.

本發明的石墨烯分散液的固體成分率G較佳為0.3質量%以上且40質量%以下。固體成分率更佳為20質量%以下，進而佳為10質量%以下，進而更佳為7質量%以下，特佳為5質量%以下。另外，固體成分率更佳為0.7質量%以上，進而佳為1質量%以上。若固體成分率為5質量%以下，則容易表現出流動性且操作性優異。若固體成分率超過40質量%，則變得容易於分散液中引起石墨烯的積層凝集，難以維持良好的分散狀態，若未滿0.3質量%，則有於在電極糊的製造中使用時因分散液中的溶劑而電極糊的固體成分率下降，黏度下降，因此塗敷性惡化的傾向。The solid content ratio G of the graphene dispersion liquid of the present invention is preferably 0.3% by mass or more and 40% by mass or less. The solid content ratio is more preferably 20% by mass or less, further preferably 10% by mass or less, further preferably 7% by mass or less, and particularly preferably 5% by mass or less. Further, the solid content ratio is more preferably 0.7% by mass or more, and still more preferably 1% by mass or more. When the solid content ratio is 5% by mass or less, fluidity is easily exhibited and the workability is excellent. When the solid content rate is more than 40% by mass, it tends to cause aggregation of graphene in the dispersion liquid, and it is difficult to maintain a good dispersion state. If it is less than 0.3% by mass, it is used in the production of the electrode paste. The solvent in the dispersion liquid and the solid content rate of the electrode paste are lowered, and the viscosity is lowered, so that the coating property tends to be deteriorated.

石墨烯分散液的固體成分率G可藉由對自石墨烯分散液使溶劑乾燥後的重量進行測定，並將測定值除以石墨烯分散液自身的重量而算出。具體而言，使石墨烯分散液1 g左右附著於重量已知的玻璃基板上，並於溫度調整為120℃的加熱板上加熱1.5小時而使溶劑揮發，對此時所殘存的石墨烯的重量進行測定而算出。The solid content ratio G of the graphene dispersion can be calculated by measuring the weight after drying the solvent from the graphene dispersion, and dividing the measured value by the weight of the graphene dispersion itself. Specifically, about 1 g of the graphene dispersion liquid was attached to a glass substrate having a known weight, and heated on a hot plate adjusted to a temperature of 120 ° C for 1.5 hours to volatilize the solvent, and the graphene remaining there was The weight was measured and calculated.

本發明的石墨烯分散液較佳為含有具有酸性基的表面處理劑（以下，有時僅稱為「表面處理劑」）。具有酸性基的表面處理劑是藉由至少其一部分附著存在於石墨烯的表面而發揮提高石墨烯的分散性的效果者。此處，所謂酸性基為羥基、酚性羥基、硝基、羧基或羰基。表面處理劑只要為具有酸性基、即羥基、酚性羥基、硝基、羧基或羰基的化合物，則並無特別限制，可為高分子化合物亦可為低分子化合物。The graphene dispersion liquid of the present invention preferably contains a surface treatment agent having an acidic group (hereinafter sometimes referred to simply as "surface treatment agent"). The surface treatment agent having an acidic group exhibits an effect of improving the dispersibility of graphene by adhering at least a part of it to the surface of graphene. Here, the acidic group is a hydroxyl group, a phenolic hydroxyl group, a nitro group, a carboxyl group or a carbonyl group. The surface treatment agent is not particularly limited as long as it is a compound having an acidic group, that is, a hydroxyl group, a phenolic hydroxyl group, a nitro group, a carboxyl group or a carbonyl group, and may be a polymer compound or a low molecular compound.

作為具有酸性基的高分子化合物，可例示聚乙烯吡咯啶酮、聚乙烯醇、聚甲基乙烯醚等。作為低分子化合物，就與石墨烯表面的親和性的觀點而言，較佳為具有芳香環的化合物。就提高石墨烯的導電性的觀點而言，相較於高分子化合物而言，較佳為低分子化合物。Examples of the polymer compound having an acidic group include polyvinylpyrrolidone, polyvinyl alcohol, and polymethyl vinyl ether. As the low molecular compound, a compound having an aromatic ring is preferred from the viewpoint of affinity with the surface of the graphene. From the viewpoint of improving the conductivity of graphene, a low molecular compound is preferable to the polymer compound.

其中，就具有對石墨烯的接著性、對溶劑的分散性的方面而言，具有兒茶酚基的化合物作為表面處理劑而言較佳。作為具有兒茶酚基的化合物，可列舉兒茶酚、多巴胺鹽酸鹽、3-(3,4-二羥基苯基)-L-丙胺酸、4-(1-羥基-2-胺基乙基)兒茶酚、3,4-二羥基苯甲酸、3,4-二羥基苯基乙酸、咖啡酸、4-甲基兒茶酚及4-第三丁基兒茶酚（4-tert-Butylpyrocatechol）。Among them, a compound having a catechol group is preferred as a surface treatment agent in terms of adhesion to graphene and dispersibility to a solvent. Examples of the compound having a catechol group include catechol, dopamine hydrochloride, 3-(3,4-dihydroxyphenyl)-L-alanine, and 4-(1-hydroxy-2-amino group B. Catechol, 3,4-dihydroxybenzoic acid, 3,4-dihydroxyphenylacetic acid, caffeic acid, 4-methylcatechol and 4-tert-butylcatechol (4-tert- Butylpyrocatechol).

作為表面處理劑的酸性基，較佳為酚性羥基。作為具有酚性羥基的化合物，可列舉苯酚、硝基苯酚、甲酚、兒茶酚及具有將該些的一部分取代的結構的化合物。The acidic group as the surface treatment agent is preferably a phenolic hydroxyl group. Examples of the compound having a phenolic hydroxyl group include phenol, nitrophenol, cresol, catechol, and a compound having a structure in which a part of these are substituted.

另外，具有酸性基的界面活性劑亦可較佳地用作表面處理劑。作為界面活性劑，可使用陽離子系界面活性劑、陰離子系界面活性劑、非離子系界面活性劑等的任一種，陰離子、陽離子其自身有時參與電氣化學反應，因此於作為電池材料而使用的情況下，較佳為未經離子化的非離子系界面活性劑。Further, a surfactant having an acidic group can also be preferably used as a surface treating agent. As the surfactant, any of a cationic surfactant, an anionic surfactant, and a nonionic surfactant can be used, and an anion or a cation sometimes participates in an electrochemical reaction, and thus is used as a battery material. In this case, a nonionic surfactant which is not ionized is preferred.

另外，表面處理劑除了酸性基以外，亦可具有鹼性基，尤其若具有胺基，則分散性進一步提高。因此，具有兒茶酚基及胺基此兩者的化合物作為表面處理劑而言特佳。作為所述化合物，可例示多巴胺鹽酸鹽。Further, the surface treatment agent may have a basic group in addition to the acidic group, and particularly if it has an amine group, the dispersibility is further improved. Therefore, a compound having both a catechol group and an amine group is particularly preferable as a surface treatment agent. As the compound, dopamine hydrochloride can be exemplified.

於將本發明的石墨烯分散液的藉由雷射繞射/散射式粒度分佈測定法所測定的石墨烯的中間值徑度設為D（μm）且將藉由利用雷射顯微鏡觀察到的石墨烯的最長徑度與最短徑度的相加平均而求出的石墨烯的面方向的大小的平均值設為S（μm）時，較佳為同時滿足下述式（3）及式（4）， 0.5 μm≦S≦15 μm ···（3） 1.0≦D/S≦3.0 ···（4）。The median diameter of graphene measured by laser diffraction/scattering particle size distribution measurement of the graphene dispersion of the present invention is set to D (μm) and will be observed by using a laser microscope. When the average value of the surface direction of the graphene obtained by adding the average of the longest diameter and the shortest diameter of the graphene is S (μm), it is preferable to satisfy the following formula (3) and formula ( 4), 0.5 μm≦S≦15 μm ···(3) 1.0≦D/S≦3.0 ···(4).

石墨烯的中間值徑度D是對應於將石墨烯分散液直接供於雷射繞射/散射式粒度分佈測定裝置而測定的粒度分佈的中央值的粒徑。具體而言，可藉由後述的測定例5中記載的方法來測定。石墨烯的面方向的大小S（最長徑度與最短徑度的平均）並無特別限制，作為下限，較佳為0.5 μm以上，更佳為0.7 μm以上，進而佳為1.0 μm以上，作為上限，較佳為15 μm以下，更佳為10 μm以下，進而佳為4 μm以下。於S未滿0.5 μm的情況下、應用於電極的情況下，有石墨烯彼此的接點的數量變多，電阻值容易增大的傾向。另外，於S大於15 μm的情況下，有石墨烯的剝離度或對溶劑的分散性低，製成電極用糊時的塗佈性下降或塗佈膜面的品質下降的擔心，有於形成電極時無法形成良好的導電路徑的可能性。The median diameter D of the graphene is a particle diameter corresponding to the median value of the particle size distribution measured by directly supplying the graphene dispersion to the laser diffraction/scattering particle size distribution measuring apparatus. Specifically, it can be measured by the method described in the measurement example 5 mentioned later. The size S of the surface direction of the graphene (the average of the longest diameter and the shortest diameter) is not particularly limited, and the lower limit is preferably 0.5 μm or more, more preferably 0.7 μm or more, and still more preferably 1.0 μm or more. It is preferably 15 μm or less, more preferably 10 μm or less, and further preferably 4 μm or less. When S is less than 0.5 μm and applied to an electrode, the number of contacts of graphene increases, and the resistance value tends to increase. In addition, when S is more than 15 μm, the peeling degree of graphene or the dispersibility to a solvent is low, and the coating property at the time of forming an electrode paste is lowered or the quality of a coating film surface is lowered, and it is formed. The possibility of a good conductive path cannot be formed when the electrode is used.

另外，於D/S未滿1.0的情況下、即石墨烯的面方向的大小S大於中間值徑度D的情況下，表示石墨烯並非為面形狀而為於溶劑中折疊的結構。該情況下，石墨烯彼此孤立，有於形成電極時無法形成良好的導電路徑的可能性。另一方面，於D/S超過3.0的情況下，表示石墨烯彼此過度凝集，難以獲得充分的剝離或分散性。D/S較佳為1.4以上且2.5以下。In the case where D/S is less than 1.0, that is, when the size S of the surface direction of graphene is larger than the intermediate diameter D, it means that the graphene is not in a planar shape and is folded in a solvent. In this case, the graphenes are isolated from each other, and there is a possibility that a good conductive path cannot be formed when the electrodes are formed. On the other hand, when D/S exceeds 3.0, it means that graphene is excessively aggregated, and it is difficult to obtain sufficient peeling or dispersibility. D/S is preferably 1.4 or more and 2.5 or less.

另外，關於本發明的石墨烯分散液，於將藉由雷射顯微鏡觀察到的石墨烯的厚度的平均值設為T（nm）時，較佳為滿足下述式（5）， 0.1≦S/T≦1.5 ···（5）。Further, in the graphene dispersion liquid of the present invention, when the average value of the thickness of the graphene observed by the laser microscope is T (nm), it is preferable to satisfy the following formula (5), 0.1 ≦S. /T≦1.5 ···(5).

石墨烯的厚度的平均值T使用以如下方式求出的值。 首先，使用NMP將石墨烯分散液稀釋為0.002質量%，滴加至玻璃基板上並進行乾燥。而且，利用可測定立體形狀的雷射顯微鏡對基板上的石墨烯進行觀察，對各石墨烯的厚度進行測定。於在一小片中存在厚度不均的情況下，求出面積平均厚度。如此隨機地算出50個石墨烯的厚度，將其平均值設為T。The average value T of the thickness of graphene is a value obtained as follows. First, the graphene dispersion was diluted to 0.002% by mass using NMP, dropped onto a glass substrate, and dried. Further, the graphene on the substrate was observed by a laser microscope capable of measuring a three-dimensional shape, and the thickness of each graphene was measured. In the case where there is thickness unevenness in a small piece, the area average thickness is obtained. The thickness of 50 graphenes was calculated at random, and the average value was defined as T.

於S/T未滿0.1的情況下，是指相對於石墨烯的面方向的大小而言，石墨烯的層方向的厚度厚的情況。該情況下，有製成電極時的導電性惡化的傾向。另外，於S/T大於1.5的情況下，是指相對於石墨烯的面方向的大小而言，石墨烯的層方向的厚度薄的情況。該情況下，有於製成分散液其自身或電極用糊的情況下的黏度增大，操作時的作業性下降之虞。於本發明的石墨烯分散液中，更佳為0.2≦S/T≦0.8。When the S/T is less than 0.1, it means that the thickness of the graphene in the layer direction is thick with respect to the size of the surface direction of the graphene. In this case, there is a tendency that the conductivity at the time of electrode formation is deteriorated. In addition, when S/T is more than 1.5, it means that the thickness of the graphene in the layer direction is thin with respect to the size of the surface direction of graphene. In this case, the viscosity of the dispersion liquid itself or the electrode paste is increased, and the workability during the operation is lowered. In the graphene dispersion of the present invention, more preferably 0.2 ≦S/T ≦ 0.8.

石墨烯的厚度T與面方向的大小S可藉由利用雷射顯微鏡或原子力顯微鏡對稀釋液於基板上展開、並進行乾燥而得的樣品進行觀察而測定。具體而言，可利用後述的測定例6及測定例7中記載的方法來測定。The thickness T of the graphene and the size S of the surface direction can be measured by observing a sample obtained by developing a diluted solution on a substrate by a laser microscope or an atomic force microscope and drying it. Specifically, it can be measured by the methods described in Measurement Example 6 and Measurement Example 7 which will be described later.

於將本發明的石墨烯分散液的利用卡爾費歇爾法測定的130℃下的含水率設為W1（質量%）、同樣地利用卡爾費歇爾法測定的250℃下的含水率設為W2（質量%）且將石墨烯的固體成分率設為G（質量%）時，（W2-W1）/G的值為0.005以上且0.05以下。The water content at 130 ° C measured by the Karl Fischer method of the graphene dispersion of the present invention is W1 (% by mass), and the water content at 250 ° C measured by the Karl Fischer method is set to When W2 (% by mass) and the solid content ratio of graphene is G (% by mass), the value of (W2-W1)/G is 0.005 or more and 0.05 or less.

此處，W1是指石墨烯分散液中的有機溶劑中所含的自由水、與吸附於石墨烯但容易脫離的吸附水的概算的合計含水率。另一方面，W2是進而將與石墨烯表面牢固地結合的即便於130℃下亦不脫離的結合水的含水率和所述自由水與吸附水的合計含水率相加而得的含水率。即，W2-W1表示與石墨烯牢固地結合的結合水的含水率的概算值。Here, W1 is a total water content of the estimated amount of free water contained in the organic solvent in the graphene dispersion and the adsorbed water which is adsorbed to the graphene but is easily detached. On the other hand, W2 is a water content obtained by further adding the water content of the bound water which does not escape at 130 ° C and the total water content of the free water and the adsorbed water, which are firmly bonded to the surface of the graphene. That is, W2-W1 represents an estimated value of the moisture content of the bound water which is firmly bonded to the graphene.

結合水經由石墨烯中所含的羥基·羧基·環氧基·羰基等而強力地結合。藉由存在所述結合水，石墨烯與有機溶劑變得容易相互作用，亦實現分散穩定化。因此，較佳為將結合水的重量相對於石墨烯重量的比控制在適當的範圍內。The bound water is strongly bonded via a hydroxyl group, a carboxyl group, an epoxy group, a carbonyl group or the like contained in the graphene. By the presence of the bound water, graphene and the organic solvent become easy to interact, and dispersion stabilization is also achieved. Therefore, it is preferred to control the ratio of the weight of the bound water to the weight of the graphene within an appropriate range.

另外，因結合水的存在亦可獲得提高石墨烯的離子傳導性的效果。石墨烯具有薄的平板狀的結構，且石墨烯平面彼此產生π-π相互作用，因此平面彼此容易積層。離子難以於無間隙地積層的石墨烯中移動。另一方面，具有適度的結合水的石墨烯有於藉由石墨烯彼此進行積層的情況下亦容易產生間隙，離子傳導路徑變多，離子傳導性提高的傾向。Further, an effect of improving the ion conductivity of graphene can also be obtained due to the presence of bound water. Graphene has a thin plate-like structure, and the graphene planes generate π-π interaction with each other, and thus the planes are easily laminated to each other. The ions are difficult to move in the graphene laminated without gaps. On the other hand, in the case of graphene having a moderate amount of bound water, when graphene is laminated with each other, a gap is likely to occur, and an ion conduction path is increased, and ion conductivity tends to be improved.

若（W2-W1）/G的值未滿0.005，則與有機溶劑的相互作用變少而容易凝集。於進入鋰離子電池的電極內的情況下，有凝集的石墨烯難以形成導電路徑且離子傳導性亦差，而妨礙充放電的傾向。另外，若（W2-W1）/G的值超過0.05，則於鋰離子電池中使用的情況下，有結合水內的一部分電解而產生氣體，從而對電池性能帶來不良影響之虞。藉由將（W2-W1）/G的值控制為0.005以上且0.05以下的範圍，可良好地分散於有機溶劑中，可兼具鋰離子電池電極內的良好的導電路徑形成與高離子傳導性。（W2-W1）/G的值較佳為0.008以上，進而佳為0.01以上。另外，（W2-W1）/G的值較佳為0.03以下，進而佳為0.02以下。When the value of (W2-W1)/G is less than 0.005, the interaction with the organic solvent is small and aggregation is easy. When entering the electrode of a lithium ion battery, it is difficult for agglomerated graphene to form a conductive path and the ion conductivity is also poor, which tends to hinder charge and discharge. Further, when the value of (W2-W1)/G exceeds 0.05, when it is used in a lithium ion battery, a part of the water in the combined water is electrolyzed to generate a gas, which adversely affects battery performance. By controlling the value of (W2-W1)/G to a range of 0.005 or more and 0.05 or less, it can be favorably dispersed in an organic solvent, and can form a good conductive path formation and high ion conductivity in a lithium ion battery electrode. . The value of (W2-W1)/G is preferably 0.008 or more, and more preferably 0.01 or more. Further, the value of (W2-W1)/G is preferably 0.03 or less, and more preferably 0.02 or less.

W1及W2是藉由卡爾費歇爾法而測定。具體而言是藉由日本工業標準（Japanese Industrial Standards，JIS）K0113：2005的8.3項中所示的水分汽化-電量滴定法而測定。測定機器並無限制，可使用市售的含水率測定器。作為所述含水率測定器，可例示平沼產業股份有限公司製造的卡爾費歇爾水分計AQ-2200等。W1 and W2 were measured by the Karl Fischer method. Specifically, it is measured by the moisture vaporization-electricity titration method shown in Section 8.3 of Japanese Industrial Standards (JIS) K0113:2005. The measuring machine is not limited, and a commercially available moisture content measuring device can be used. As the water content measuring device, a Karl Fischer moisture meter AQ-2200 manufactured by Hiranuma Sangyo Co., Ltd., or the like can be exemplified.

本發明的石墨烯分散液中所含的石墨烯的藉由布厄特（Brunauer-Emmett-Tellern，BET）測定法所測定的比表面積（以下，有時僅稱為「比表面積」）較佳為80 m2 /g以上且250 m2 /g以下。石墨烯的比表面積反映石墨烯的厚度與石墨烯的剝離度，越大則表示石墨烯越薄，剝離度越高。若石墨烯的比表面積未滿80 m2 /g，則有難以形成導電性網路的傾向，若大於250 m2 /g，則有分散性下降的傾向。石墨烯的比表面積更佳為100 m2 /g以上，進而更佳為130 m2 /g以上。另外同樣地，較佳為200 m2 /g以下，更佳為180 m2 /g以下。再者，BET測定法為對藉由真空乾燥機或凍結乾燥機等將石墨烯分散液預備乾燥後的乾燥試樣利用JIS Z8830：2013內記載的方法而進行，吸附氣體量的測定方法為利用載氣法而進行，吸附資料的解析為利用一點法而進行。The specific surface area (hereinafter, simply referred to as "specific surface area") of the graphene contained in the graphene dispersion of the present invention measured by a Brunauer-Emmett-Tellern (BET) measurement method is preferably 80 m 2 /g or more and 250 m 2 /g or less. The specific surface area of graphene reflects the thickness of graphene and the degree of peeling of graphene. The larger the graphene, the thinner the graphene and the higher the peeling degree. When the specific surface area of graphene is less than 80 m 2 /g, it tends to be difficult to form a conductive network, and if it exceeds 250 m 2 /g, the dispersibility tends to decrease. The specific surface area of the graphene is more preferably 100 m 2 /g or more, and still more preferably 130 m 2 /g or more. Further, similarly, it is preferably 200 m 2 /g or less, more preferably 180 m 2 /g or less. In the BET measurement method, the dried sample obtained by preliminarily drying the graphene dispersion by a vacuum dryer or a freeze dryer is carried out by the method described in JIS Z8830:2013, and the measurement method of the amount of adsorbed gas is utilized. The carrier gas method was carried out, and the analysis of the adsorption data was carried out by a one-point method.

本發明的石墨烯分散液的（W2-W1）/G的值除以石墨烯的藉由BET測定法所測定的比表面積所得的值較佳為0.000025 g/m2 以上且0.00025 g/m2 以下。（W2-W1）/G除以比表面積所得的值表示石墨烯每單位表面積的結合水的重量。若結合水於石墨烯單位表面積中所佔的比例過高，則石墨烯不能完全保持結合水而容易引起水的電解。若結合水於石墨烯單位表面積中所佔的比例過低，則有石墨烯分散液的分散穩定性變差的傾向。（W2-W1）/G除以比表面積所得的值更佳為0.000035 g/m2 以上且0.00015 g/m2 以下，進而佳為0.000050 g/m2 以上且0.00010 g/m2 以下。The value of (W2-W1)/G of the graphene dispersion of the present invention divided by the specific surface area measured by the BET measurement of graphene is preferably 0.000025 g/m 2 or more and 0.00025 g/m 2 . the following. The value obtained by dividing (W2-W1)/G by the specific surface area represents the weight of the bound water per unit surface area of the graphene. If the proportion of bound water in the surface area per unit of graphene is too high, graphene cannot completely retain bound water and easily cause electrolysis of water. When the proportion of the bound water in the surface area per unit area of the graphene is too low, the dispersion stability of the graphene dispersion tends to be deteriorated. The value obtained by dividing the specific surface area of (W2-W1)/G is more preferably 0.000035 g/m 2 or more and 0.00015 g/m 2 or less, further preferably 0.000050 g/m 2 or more and 0.0001 g/m 2 or less.

作為本發明的石墨烯分散液的溶劑，使用含有50質量%以上的N-甲基吡咯啶酮的溶劑。N-甲基吡咯啶酮中所含的內醯胺結構與胺基、硝基等含氮官能基的親和性、與水分的親和性均高。如後所述般，可較佳地使用表面存在氮者作為石墨烯，該情況下，有於石墨烯結合水、氮及N-甲基吡咯啶酮三者間進行相互作用而形成良好的分散狀態的傾向。As a solvent of the graphene dispersion liquid of the present invention, a solvent containing 50% by mass or more of N-methylpyrrolidone is used. The intrinsic amine structure contained in the N-methylpyrrolidone has high affinity with nitrogen-containing functional groups such as an amine group and a nitro group, and has a high affinity with water. As described later, it is preferable to use nitrogen as a graphene on the surface, in which case a good dispersion is formed by interaction between graphene-bound water, nitrogen, and N-methylpyrrolidone. The tendency of the state.

作為石墨烯分散液中所含的NMP以外的溶劑，較佳為偶極矩為3.0德拜（Debye）以上的有機溶劑。作為所述溶劑，可例示γ-丁內酯、二甲基乙醯胺、二甲基甲醯胺、二甲基亞碸、乙腈等。另外，由於揮發性高的溶劑難以進行穩定的操作，因此較佳為高沸點的溶劑。NMP以外的溶劑的沸點較佳為150℃以上，進而佳為180℃以上。The solvent other than NMP contained in the graphene dispersion liquid is preferably an organic solvent having a dipole moment of 3.0 debye or more. The solvent may, for example, be γ-butyrolactone, dimethylacetamide, dimethylformamide, dimethylhydrazine or acetonitrile. Further, since a solvent having a high volatility is difficult to carry out a stable operation, a solvent having a high boiling point is preferred. The solvent other than NMP preferably has a boiling point of 150 ° C or higher, and more preferably 180 ° C or higher.

本發明的石墨烯分散液中存在的石墨烯的藉由X射線光電子分光法所測定的氧相對於碳的元素比（O/C比）較佳為0.05以上且0.40以下。於X射線光電子分光法中，藉由真空乾燥機或凍結乾燥機等對石墨烯分散液進行預備乾燥後，將乾燥試樣導入至帶有高真空腔室的測定室中，對置於超高真空中的試樣表面照射軟X射線，利用分析儀對自表面所放出的光電子進行檢測。利用寬掃描及窄掃描對所述光電子進行測定，求出物質中的束縛電子的鍵能值，藉此可獲得物質表面的元素資訊。The elemental ratio (O/C ratio) of oxygen to carbon measured by X-ray photoelectron spectroscopy of the graphene present in the graphene dispersion of the present invention is preferably 0.05 or more and 0.40 or less. In the X-ray photoelectron spectroscopy, the graphene dispersion is preliminarily dried by a vacuum dryer or a freeze dryer, and then the dried sample is introduced into a measurement chamber having a high vacuum chamber, and placed in a super high The surface of the sample in a vacuum is irradiated with soft X-rays, and the photoelectrons emitted from the surface are detected by an analyzer. The photoelectrons are measured by a wide scan and a narrow scan to determine the bond energy of the bound electrons in the substance, thereby obtaining elemental information on the surface of the substance.

已知若藉由X射線光電子分光法對本發明的石墨烯分散液進行測定，則於284 eV附近檢測到來源於碳的C1s波峰，於碳與氧鍵結的情況下移動至高能側。具體而言，基於碳與氧未鍵結的C-C鍵、C=C雙鍵、C-H鍵的波峰不移動而於284 eV附近受到檢測，於C-O單鍵的情況下於286.5 eV附近移動，於C=O雙鍵的情況下於287.5 eV附近移動，於COO鍵的情況下於288.5 eV附近移動。因此，來源於碳的信號以284 eV附近、286.5 eV附近、287.5 eV附近、288.5 eV附近的各波峰重疊的形式受到檢測。另外，同時於402 eV附近檢測到來源於氮的N1s波峰，於533 eV附近檢測到來源於氧的O1s波峰。進而，可根據C1s波峰與O1s波峰的峰值面積求出O/C比。It is known that when the graphene dispersion of the present invention is measured by X-ray photoelectron spectroscopy, a C1s peak derived from carbon is detected in the vicinity of 284 eV, and is moved to a high energy side in the case where carbon and oxygen are bonded. Specifically, the peaks of the CC bond, the C=C double bond, and the CH bond, which are not bonded by carbon and oxygen, are detected at around 284 eV without moving, and are moved around 286.5 eV in the case of a single CO bond. In the case of the =O double bond, it moves around 287.5 eV, and in the case of the COO key, it moves around 288.5 eV. Therefore, the signal derived from carbon is detected in the form of overlapping peaks near 284 eV, around 286.5 eV, around 287.5 eV, and around 288.5 eV. In addition, a nitrogen-derived N1s peak was detected near 402 eV, and an oxygen-derived O1s peak was detected near 533 eV. Further, the O/C ratio can be obtained from the peak areas of the C1s peak and the O1s peak.

石墨烯表面的氧原子是與石墨烯自身鍵結的酸性基或附著於石墨烯表面的表面處理劑所具有的酸性基中所含的氧原子。所述酸性基可提高石墨烯的分散狀態且成為結合水與石墨烯結合的接點。若石墨烯表面的酸性基過少，則分散性變差，若過多，則導電性下降而使作為導電助劑的性能變差。石墨烯的O/C比更佳為0.07以上，進而佳為0.09以上，特佳為0.10以上。另外同樣地，更佳為0.30以下，進而佳為0.20以下，特佳為0.15以下。The oxygen atom on the surface of the graphene is an oxygen atom contained in an acidic group which is bonded to the graphene itself or an acidic group which is attached to the surface treatment agent of the graphene surface. The acidic group can increase the dispersion state of graphene and become a junction of bound water and graphene. When the acid group on the surface of the graphene is too small, the dispersibility is deteriorated, and if it is too large, the conductivity is lowered to deteriorate the performance as a conductive auxiliary agent. The O/C ratio of graphene is more preferably 0.07 or more, further preferably 0.09 or more, and particularly preferably 0.10 or more. Further, in the same manner, it is more preferably 0.30 or less, further preferably 0.20 or less, and particularly preferably 0.15 or less.

石墨烯的O/C比可藉由改變成為原料的氧化石墨烯的氧化度或改變表面處理劑的量來控制。氧化石墨烯的氧化度越高，則還原後殘存的氧的量越變多，若氧化度低，則還原後的氧原子量變少。另外，藉由增加具有酸性基的表面處理劑的附著量可使氧原子量增多。The O/C ratio of graphene can be controlled by changing the degree of oxidation of graphene oxide as a raw material or changing the amount of surface treatment agent. The higher the degree of oxidation of graphene oxide, the greater the amount of oxygen remaining after reduction, and the lower the degree of oxidation, the smaller the amount of oxygen atoms after reduction. Further, the amount of oxygen atoms can be increased by increasing the amount of adhesion of the surface treatment agent having an acidic group.

另外，分散液中存在的石墨烯的藉由X射線光電子分光法所測定的氮相對於碳的元素比（N/C比）較佳為0.005以上且0.030以下，進而佳為0.010以上且0.025以下。石墨烯表面的氮原子為來源於表面處理劑中所含的胺基、硝基等含氮的官能基、或者吡啶基或咪唑基等含氮的雜環者。就提高石墨烯的分散性而言，所述含氮基較佳為適度地含有。若石墨烯的N/C比超過0.030，則氮原子取代石墨烯共軛結構，因此容易成為低導電性。另一方面，含有氮元素的表面處理劑有助於石墨烯分散性，因此較佳為少量存在。再者，N/C比與O/C比同樣地可根據C1s波峰與N1s波峰的峰值面積來求出。In addition, the element ratio (N/C ratio) of nitrogen to carbon measured by X-ray photoelectron spectroscopy of the graphene present in the dispersion is preferably 0.005 or more and 0.030 or less, and more preferably 0.010 or more and 0.025 or less. . The nitrogen atom on the surface of the graphene is derived from a nitrogen-containing functional group such as an amine group or a nitro group contained in the surface treatment agent, or a nitrogen-containing heterocyclic ring such as a pyridyl group or an imidazolyl group. In order to improve the dispersibility of graphene, the nitrogen-containing group is preferably contained moderately. When the N/C ratio of graphene exceeds 0.030, the nitrogen atom replaces the graphene conjugated structure, and thus it is likely to have low conductivity. On the other hand, the surface treatment agent containing a nitrogen element contributes to the dispersibility of graphene, and therefore it is preferably present in a small amount. Further, the N/C ratio can be obtained from the peak area of the C1s peak and the N1s peak in the same manner as the O/C ratio.

＜石墨烯分散液的製造方法＞ 本發明的石墨烯分散液可藉由如下石墨烯分散液的製造方法來製作，所述製造方法包括： 還原步驟，包括對含有水的分散媒中所分散的氧化石墨烯進行還原； NMP混合步驟，包括將還原步驟中所獲得的中間體分散液與含有50質量%以上的N-甲基吡咯啶酮的溶劑（含NMP的溶劑）加以混合； 強力攪拌步驟，包括以剪切速度為每秒5000～每秒50000對NMP混合步驟中所獲得的中間體分散液進行攪拌； 水分去除步驟，包括藉由將含NMP的溶劑添加與吸引過濾加以組合的手法或者蒸餾而自中間體分散液中去除至少一部分水分。<Method for Producing Graphene Dispersion Liquid> The graphene dispersion liquid of the present invention can be produced by a method for producing a graphene dispersion liquid, the production method comprising: a reduction step including dispersion in a dispersion medium containing water The graphene oxide is subjected to reduction; the NMP mixing step comprises mixing the intermediate dispersion obtained in the reduction step with a solvent (NMP-containing solvent) containing 50% by mass or more of N-methylpyrrolidone; , comprising: stirring the intermediate dispersion obtained in the NMP mixing step at a shear rate of 5000 to 50,000 per second; the moisture removal step includes a method of combining NMP-containing solvent addition and suction filtration or At least a portion of the water is removed from the intermediate dispersion by distillation.

若一旦使分散液乾燥，則石墨烯層間的凝集變強，因此對於石墨烯分散液的良分散化而言特別有效的是一次也不使石墨烯乾燥地進行自還原步驟起的所有步驟（於還原步驟前進行後述的微細化步驟及/或表面處理步驟的情況下為包括所述步驟的所有步驟）。When the dispersion is dried, the aggregation between the graphene layers becomes strong, and therefore, it is particularly effective for the good dispersion of the graphene dispersion to perform all the steps from the self-reduction step without drying the graphene once. In the case where the miniaturization step and/or the surface treatment step described later are performed before the reduction step, all the steps including the steps are included.

[氧化石墨烯的製作法] 氧化石墨烯的製作法並無特別限定，可使用Hummers法等公知的方法。另外，亦可購買市售的氧化石墨烯。作為氧化石墨烯的製作方法，以下例示使用Hummers法的情況。[Method for Producing Graphene Oxide] The method for producing graphene oxide is not particularly limited, and a known method such as the Hummers method can be used. In addition, commercially available graphene oxide can also be purchased. As a method of producing graphene oxide, the case of using the Hummers method will be exemplified below.

將石墨（石墨粉）與硝酸鈉放入濃硫酸中，一面進行攪拌，一面以溫度不上升的方式緩緩添加高錳酸鉀，於25℃～50℃下攪拌反應0.2小時～5小時。其後，加入離子交換水進行稀釋並製成懸浮液，於80℃～100℃下反應5分鐘～50分鐘。最後，加入過氧化氫與脫離子水並反應1分鐘～30分鐘，而獲得氧化石墨烯分散液。將所獲得的氧化石墨烯分散液過濾、清洗而獲得氧化石墨烯凝膠。亦可對所述氧化石墨烯凝膠進行稀釋，並進行與表面處理劑的混合處理或還原處理。When graphite (graphite powder) and sodium nitrate are placed in concentrated sulfuric acid, potassium permanganate is gradually added so that the temperature does not rise, and the reaction is stirred at 25 to 50 ° C for 0.2 to 5 hours. Thereafter, ion-exchanged water is added for dilution to prepare a suspension, which is reacted at 80 ° C to 100 ° C for 5 minutes to 50 minutes. Finally, hydrogen peroxide and deionized water are added and reacted for 1 minute to 30 minutes to obtain a graphene oxide dispersion. The obtained graphene oxide dispersion liquid was filtered and washed to obtain a graphene oxide gel. The graphene oxide gel may also be diluted and subjected to a mixing treatment or a reduction treatment with a surface treatment agent.

成為氧化石墨烯的原料的石墨可為人造石墨、天然石墨的任一種，但較佳為使用天然石墨。成為原料的石墨的網目數較佳為20000以下，進而佳為5000以下。The graphite which is a raw material of graphene oxide may be either artificial graphite or natural graphite, but natural graphite is preferably used. The number of meshes of the graphite to be a raw material is preferably 20,000 or less, and more preferably 5,000 or less.

關於各反應物的比例，作為一例為相對於石墨10 g，濃硫酸為150 ml～300 ml，硝酸鈉為2 g～8 g，高錳酸鉀為10 g～40 g，過氧化氫為40 g～80 g。於加入硝酸鈉與高錳酸鉀時，利用冰浴控制溫度。於加入過氧化氫與脫離子水時，脫離子水的質量為過氧化氫質量的10倍～20倍。濃硫酸較佳為利用質量含量為70%以上者，進而佳為利用97%以上者。The ratio of each reactant is, for example, 10 g of graphite, 150 ml to 300 ml of concentrated sulfuric acid, 2 g to 8 g of sodium nitrate, 10 g to 40 g of potassium permanganate, and 40 g of hydrogen peroxide. g ~ 80 g. When adding sodium nitrate and potassium permanganate, the temperature was controlled by an ice bath. When hydrogen peroxide and deionized water are added, the mass of the deionized water is 10 to 20 times the mass of the hydrogen peroxide. The concentrated sulfuric acid is preferably one in which the mass content is 70% or more, and more preferably 97% or more.

氧化石墨烯具有高分散性，但其自身為絕緣性而無法用於導電助劑等中。若氧化石墨烯的氧化度過高，則有進行還原而獲得的石墨烯粉末的導電性變差的情況，因此氧化石墨烯的藉由X射線光電子分光法所測定的碳原子相對於氧原子的比例較佳為0.5以上。於利用X射線光電子分光法對氧化石墨烯進行測定時，於使溶劑充分乾燥的狀態下進行。Graphene oxide has high dispersibility, but it is inherently insulative and cannot be used in a conductive auxiliary agent or the like. When the degree of oxidation of graphene oxide is too high, the conductivity of the graphene powder obtained by reduction may be deteriorated. Therefore, the carbon atom of the graphene oxide measured by X-ray photoelectron spectroscopy is relative to the oxygen atom. The ratio is preferably 0.5 or more. When the graphene oxide is measured by X-ray photoelectron spectroscopy, it is carried out in a state where the solvent is sufficiently dried.

另外，若石墨未被氧化至內部，則於進行還原時，難以獲得薄片狀的石墨烯粉末。因此，理想的是於使氧化石墨烯乾燥並進行X射線繞射測定時，未檢測到石墨所特有的波峰。Further, when graphite is not oxidized to the inside, it is difficult to obtain a flaky graphene powder at the time of reduction. Therefore, it is desirable that when the graphene oxide is dried and subjected to X-ray diffraction measurement, no peak characteristic of graphite is detected.

氧化石墨烯的氧化度可藉由使石墨的氧化反應中所使用的氧化劑的量變化而調整。具體而言，氧化反應時所使用的硝酸鈉及高錳酸鉀相對於石墨的量越多則氧化度越高，越少則氧化度越低。硝酸鈉相對於石墨的重量比並無特別限定，較佳為0.200以上且0.800以下，更佳為0.250以上且0.500以下，進而佳為0.275以上且0.425以下。高錳酸鉀相對於石墨的比並無特別限定，較佳為1.00以上，更佳為1.40以上，進而佳為1.65以上。另外，較佳為4.00以下，更佳為3.00以下，進而佳為2.55以下。The degree of oxidation of graphene oxide can be adjusted by changing the amount of the oxidizing agent used in the oxidation reaction of graphite. Specifically, the more the amount of sodium nitrate and potassium permanganate used in the oxidation reaction with respect to graphite, the higher the degree of oxidation, and the smaller the degree of oxidation, the lower the degree of oxidation. The weight ratio of sodium nitrate to graphite is not particularly limited, but is preferably 0.200 or more and 0.800 or less, more preferably 0.250 or more and 0.500 or less, and still more preferably 0.275 or more and 0.425 or less. The ratio of potassium permanganate to graphite is not particularly limited, but is preferably 1.00 or more, more preferably 1.40 or more, and still more preferably 1.65 or more. Further, it is preferably 4.00 or less, more preferably 3.00 or less, and still more preferably 2.55 or less.

[還原步驟] 於還原步驟中，將含有水的分散媒中所分散的氧化石墨烯還原成石墨烯。[Reduction Step] In the reduction step, the graphene oxide dispersed in the dispersion medium containing water is reduced to graphene.

作為含有水的分散媒，可僅為水，亦可含有水以外的溶劑。作為水以外的溶劑，較佳為極性溶劑，可列舉乙醇、甲醇、1-丙醇、2-丙醇、N-甲基吡咯啶酮、二甲基甲醯胺、二甲基乙醯胺、二甲基亞碸、γ-丁內酯或所述混合物等作為較佳例。The water-containing dispersion medium may be water alone or a solvent other than water. Examples of the solvent other than water include polar solvents, and examples thereof include ethanol, methanol, 1-propanol, 2-propanol, N-methylpyrrolidone, dimethylformamide, and dimethylacetamide. Dimethyl sulfonium, γ-butyrolactone or the like and the like are preferred examples.

對氧化石墨烯進行還原的方法並無特別限定，較佳為化學還原。於化學還原的情況下，作為還原劑，可列舉有機還原劑、無機還原劑，就還原後的清洗的容易度而言，更佳為無機還原劑。The method for reducing the graphene oxide is not particularly limited, and is preferably chemical reduction. In the case of chemical reduction, examples of the reducing agent include an organic reducing agent and an inorganic reducing agent, and more preferably an inorganic reducing agent in terms of easiness of washing after reduction.

作為有機還原劑，可列舉醛系還原劑、肼衍生物還原劑、醇系還原劑，其中，由於醇系還原劑可較穩定地進行還原，因此特佳。作為醇系還原劑，可列舉甲醇、乙醇、丙醇、異丙醇、丁醇、苄醇、苯酚、乙醇胺、乙二醇、丙二醇、二乙二醇等。Examples of the organic reducing agent include an aldehyde reducing agent, a hydrazine derivative reducing agent, and an alcohol-based reducing agent. Among them, the alcohol-based reducing agent is particularly preferable because it can be stably reduced. Examples of the alcohol-based reducing agent include methanol, ethanol, propanol, isopropanol, butanol, benzyl alcohol, phenol, ethanolamine, ethylene glycol, propylene glycol, and diethylene glycol.

作為無機還原劑，可列舉二亞硫磺酸鈉、二亞硫磺酸鉀、亞磷酸、硼氫化鈉、肼等，其中，二亞硫磺酸鈉、二亞硫磺酸鉀相較而言可一面保持酸性基一面進行還原，故而可製造對溶劑的分散性高的石墨烯，可較佳地使用。Examples of the inorganic reducing agent include sodium disulfite, potassium disulfite, phosphorous acid, sodium borohydride, hydrazine, and the like. Among them, sodium disulfite and potassium disulfite are relatively acidic. Since the base is reduced, it is possible to produce graphene having high dispersibility in a solvent, and it can be preferably used.

[清洗步驟] 於結束還原步驟後，較佳為進行利用水稀釋並加以過濾的清洗步驟，藉此可獲得石墨烯分散於水中而得的凝膠狀的分散液。再者，於本說明書中，為了方便起見，將除了最終完成的本發明的石墨烯分散液以外的、石墨烯或氧化石墨烯為分散於某種分散媒中的狀態下的製造途中的中間體，包含凝膠狀者在內全部稱為「中間體分散液」。[Cleaning Step] After the completion of the reduction step, it is preferred to carry out a washing step of diluting with water and filtering, whereby a gel-like dispersion obtained by dispersing graphene in water can be obtained. In addition, in the present specification, for the sake of convenience, in addition to the graphene dispersion of the present invention which is finally completed, graphene or graphene oxide is dispersed in a certain dispersion medium in the middle of the manufacturing process. The body, including the gel, is referred to as "intermediate dispersion".

[表面處理步驟] 可視需要於還原步驟的前後或進行中添加將與具有酸性基的表面處理劑混合的表面處理步驟。作為表面處理劑，可使用上文所述者。[Surface Treatment Step] It is possible to add a surface treatment step to be mixed with a surface treatment agent having an acidic group before or during or after the reduction step. As the surface treatment agent, those described above can be used.

為了良好地將氧化石墨烯與表面處理劑加以混合，較佳為於氧化石墨烯或還原後的石墨烯與表面處理劑的任一者分散於溶劑（分散媒）中的狀態下加以混合。此時，較佳為氧化石墨烯與表面處理劑均完全溶解的情況，亦可一部分不溶解而以固體的狀態進行分散。作為溶劑，較佳為極性溶劑，但並無特別限定，可列舉水、乙醇、甲醇、1-丙醇、2-丙醇、N-甲基吡咯啶酮、二甲基甲醯胺、二甲基乙醯胺、二甲基亞碸、γ-丁內酯或所述混合物等。In order to satisfactorily mix the graphene oxide with the surface treatment agent, it is preferred to mix the graphene oxide or the graphene after the reduction and the surface treatment agent in a state of being dispersed in a solvent (dispersion medium). In this case, it is preferred that both the graphene oxide and the surface treatment agent are completely dissolved, or a part of the graphene oxide may be dissolved in a solid state without being dissolved. The solvent is preferably a polar solvent, but is not particularly limited, and examples thereof include water, ethanol, methanol, 1-propanol, 2-propanol, N-methylpyrrolidone, dimethylformamide, and dimethyl. Ethyl amide, dimethyl hydrazine, γ-butyrolactone or the like.

[微細化步驟] 亦可視需要於還原步驟的前後或進行中添加將氧化石墨烯或還原後的石墨烯微細化的微細化步驟。作為微細化步驟中的溶劑，可使用與表面處理步驟中所述者相同的溶劑。就較佳為於將氧化石墨烯微細化的狀態下進行還原步驟的方面而言，微細化步驟更佳為於還原步驟之前或還原步驟的進行中進行。[Minization Step] It is also possible to add a refining step of refining graphene oxide or reduced graphene before or during or after the reduction step. As the solvent in the miniaturization step, the same solvent as that described in the surface treatment step can be used. In the aspect of performing the reduction step in a state where the graphene oxide is refined, the refining step is more preferably performed before the reduction step or during the reduction step.

藉由添加微細化步驟，可使氧化石墨烯或石墨烯的面方向的大小S為適當的大小。作為進行微細化的手法，並無特別限定，於藉由將多個珠或球等粉碎介質與分散液混合並使粉碎介質彼此碰撞而使氧化石墨烯或石墨烯粉碎並分散的手法的情況下，引發氧化石墨烯或石墨烯彼此的凝集，因此可較佳地使用不利用粉碎介質而賦予分散液強剪切力的無介質分散法。作為例子，可列舉：將施加了壓力的中間體分散液與單體的陶瓷球碰撞的手法、或者利用使施加了壓力的中間體分散液彼此碰撞而進行分散的液-液剪切型的濕式噴射磨機的手法。另外，對中間體分散液施加超音波的手法亦為無介質分散法且為較佳的手法。於微細化步驟中，無介質分散法的處理壓力或輸出功率越高，則氧化石墨烯或石墨烯越具有微細化的傾向，處理時間越長，則越具有微細化的傾向。較佳的石墨烯的面方向的大小S如之前所述般。可藉由微細化步驟中的微細化處理的種類·處理條件·處理時間來製備還原後的石墨烯的大小。By adding the miniaturization step, the size S of the surface direction of the graphene oxide or graphene can be made an appropriate size. The method of miniaturization is not particularly limited, and in the case of a method in which a plurality of beads or a pulverization medium such as a ball is mixed with a dispersion liquid and the pulverization medium collides with each other to pulverize and disperse graphene oxide or graphene. Since the aggregation of graphene oxide or graphene is initiated, it is preferable to use a medium-free dispersion method which imparts a strong shearing force to the dispersion without using the pulverization medium. As an example, a method of colliding a pressure-dispersed intermediate dispersion with a single ceramic ball or a liquid-liquid shear type dispersion in which an intermediate dispersion to which pressure is applied collides with each other is exemplified. The method of jet mill. Further, the method of applying ultrasonic waves to the intermediate dispersion is also a medium-free dispersion method and is a preferred method. In the miniaturization step, the higher the treatment pressure or the output power of the medium-free dispersion method, the more the graphene oxide or the graphene tends to be finer, and the longer the treatment time, the more the fineness tends to be. The size S of the surface direction of the preferred graphene is as described above. The size of the graphene after reduction can be prepared by the type, processing conditions, and treatment time of the miniaturization treatment in the miniaturization step.

[NMP混合步驟] 為了將經過還原步驟的中間體分散液的水置換為有機溶劑，而進行將中間體分散液與含有50質量%以上的NMP的溶劑（以下，有時僅稱為「含NMP的溶劑」）加以混合的NMP混合步驟。於NMP混合步驟中，將還原步驟中所獲得的中間體分散液、或者視需要對還原步驟中所獲得的中間體分散液進行清洗步驟、表面處理步驟及/或微細化步驟而得的中間體分散液與含NMP的溶劑直接混合。即，自還原步驟結束後至NMP混合步驟中的與含NMP的溶劑的混合為止，中間體分散液始終為分散液的狀態，並不進行將分散媒自中間體分散液去除而以粉末狀態回收石墨烯的凍結乾燥等操作。[NMP mixing step] In order to replace the water in the intermediate dispersion in the reduction step with an organic solvent, the intermediate dispersion liquid and a solvent containing 50% by mass or more of NMP are used (hereinafter, simply referred to as "NMP-containing" Solvent") NMP mixing step of mixing. In the NMP mixing step, the intermediate dispersion obtained in the reduction step, or the intermediate dispersion obtained in the reduction step, if necessary, is subjected to a washing step, a surface treatment step, and/or a refining step. The dispersion is mixed directly with the solvent containing NMP. That is, the intermediate dispersion liquid is always in a state of a dispersion from the end of the reduction step to the mixing with the NMP-containing solvent in the NMP mixing step, and the dispersion medium is not removed from the intermediate dispersion and is recovered in a powder state. Operation of freeze-drying of graphene.

作為含NMP的溶劑，除了NMP其自身以外，只要NMP的比率為50質量%以上，則亦可使用進而含有乙醇、甲醇、1-丙醇、2-丙醇、N-甲基吡咯啶酮、二甲基甲醯胺、二甲基乙醯胺、二甲基亞碸、γ-丁內酯、乙腈、丙酮等極性溶劑的溶劑。若溶劑中的NMP的比率未滿50質量%，則有溶劑中的石墨烯的分散性下降的傾向。The NMP-containing solvent may be used in addition to NMP itself, and may further contain ethanol, methanol, 1-propanol, 2-propanol or N-methylpyrrolidone as long as the ratio of NMP is 50% by mass or more. A solvent for a polar solvent such as dimethylformamide, dimethylacetamide, dimethylhydrazine, γ-butyrolactone, acetonitrile or acetone. When the ratio of NMP in the solvent is less than 50% by mass, the dispersibility of graphene in the solvent tends to decrease.

將還原步驟結束後的中間體分散液與含NMP的溶劑混合時的混合比並無特別限定，若混合的含NMP的溶劑過少，則混合液成為高黏度，因此操作困難，若混合的含NMP的溶劑過多，則每單位處理量的石墨烯量變少，因此處理效率變差。就獲得操作容易的低黏度的分散液且使處理效率良好的觀點而言，相對於還原步驟結束後的中間體分散液100質量份，以較佳為混合含NMP的溶劑10質量份～3000質量份、更佳為20質量份～2000質量份、進而佳為50質量份～1500質量份為宜。The mixing ratio of the intermediate dispersion liquid after the completion of the reduction step and the NMP-containing solvent is not particularly limited. If the mixed NMP-containing solvent is too small, the mixed liquid has a high viscosity, so that handling is difficult, and if mixed NMP-containing If the amount of the solvent is too large, the amount of graphene per unit throughput becomes small, and thus the treatment efficiency is deteriorated. From the viewpoint of obtaining a low-viscosity dispersion which is easy to handle and improving the treatment efficiency, it is preferable to mix 10 parts by mass to 3000 mass of the NMP-containing solvent with respect to 100 parts by mass of the intermediate dispersion liquid after completion of the reduction step. The amount is preferably from 20 parts by mass to 2,000 parts by mass, more preferably from 50 parts by mass to 1,500 parts by mass.

[強力攪拌步驟] 其次，進行以剪切速度為每秒5000～每秒50000對NMP混合步驟後的中間體分散液進行攪拌處理的步驟（強力攪拌步驟）。藉由利用強力攪拌步驟將石墨烯剝離，可消除石墨烯彼此的積層凝集。再者，於本說明書中，將對中間體分散液賦予所述剪切力的旋轉刀片攪拌機稱為「高剪切攪拌機」。[Strong Stirring Step] Next, a step of stirring the intermediate dispersion liquid after the NMP mixing step at a shear rate of 5,000 to 50,000 per second (strong stirring step) is performed. By peeling off the graphene by a strong stirring step, the agglomeration of the graphenes with each other can be eliminated. Further, in the present specification, a rotary blade mixer that imparts the shearing force to the intermediate dispersion is referred to as a "high shear mixer".

強力攪拌步驟的剪切速度為每秒5000～每秒50000。剪切速度是攪拌機的旋轉刀片的最大徑的周速除以攪拌機旋轉刀片前端（決定最大徑的刀片前端）距壁面的距離所得的值。攪拌機的旋轉刀片的周速是定義為周長×旋轉速度。若剪切速度過小，則不易引起石墨烯的剝離，石墨烯的剝離度降低。另一方面，若剪切速度過大，則石墨烯的剝離度變得過高，分散性下降。剪切速度較佳為每秒10000以上，更佳為每秒20000以上。另外同樣地，較佳為每秒45000以下，更佳為每秒40000以下。另外，強力攪拌步驟的處理時間較佳為15秒～300秒，更佳為20秒～120秒，進而佳為30秒～80秒。The shearing speed of the vigorous stirring step is 5000 to 50,000 per second. The shear rate is a value obtained by dividing the peripheral speed of the maximum diameter of the rotary blade of the agitator by the distance from the wall surface of the front end of the agitator rotating blade (the blade tip determining the maximum diameter). The peripheral speed of the rotating blade of the mixer is defined as the circumference x the rotation speed. When the shear rate is too small, peeling of graphene is less likely to occur, and the peeling degree of graphene is lowered. On the other hand, if the shear rate is too large, the peeling degree of graphene becomes too high, and the dispersibility falls. The shearing speed is preferably 10,000 or more per second, more preferably 20,000 or more per second. Further, similarly, it is preferably 45,000 or less per second, and more preferably 40,000 or less per second. Further, the treatment time of the vigorous stirring step is preferably from 15 seconds to 300 seconds, more preferably from 20 seconds to 120 seconds, and still more preferably from 30 seconds to 80 seconds.

強力攪拌步驟中使用的高剪切攪拌機為薄膜回旋方式、轉子/定子式等旋轉的刀片與壁面的距離為10 mm以下的短形狀，較佳為無介質方式的攪拌機。作為所述攪拌機，例如可列舉：菲萊密克司（filmix）（註冊商標）30-30型（譜萊密克司（primix）公司製造）、克萊密克司（clearmix）（註冊商標）CLM-0.8S（M.技術（M.Technique）公司製造）、超級剪切機（super shear mixer）SDRT0.35-0.75（佐竹化學機械工業公司製造）等。The high-shear mixer used in the strong stirring step is a short shape in which the distance between the rotating blade of the film and the rotor/stator type is 10 mm or less, and preferably a mediumless mixer. As the agitator, for example, filmix (registered trademark) type 30-30 (manufactured by primix), clearmix (registered trademark) CLM-0.8 S (M. Technique), super shear mixer SDRT 0.35-0.75 (manufactured by Satake Chemical Industry Co., Ltd.), and the like.

[水分去除步驟] 水分去除步驟是藉由將含NMP的溶劑添加與吸引過濾加以組合的手法或者蒸餾而去除中間體分散液中所含的至少一部分水分的步驟。於加壓過濾或離心分離般的對分散液中所含的石墨烯施加強力的溶劑去除方法中，有石墨烯積層凝集的傾向，而欠佳。水分去除步驟較佳為於強力攪拌步驟結束後的任意階段進行，若為NMP混合步驟後，則亦可於強力攪拌步驟前進行。[Moisture Removal Step] The moisture removal step is a step of removing at least a part of moisture contained in the intermediate dispersion by a method of adding NMP-containing solvent and suction filtration, or by distillation. In the solvent removal method which applies a strong force to the graphene contained in the dispersion liquid by pressure filtration or centrifugation, the graphene layer tends to aggregate, which is not preferable. The moisture removal step is preferably carried out at any stage after the completion of the vigorous stirring step, and may be carried out before the vigorous stirring step after the NMP mixing step.

作為將水分去除步驟中的含NMP的溶劑添加與吸引過濾加以組合的手法，較佳為於在中間體分散液中添加含NMP的溶劑並攪拌後，進行減壓吸引過濾。減壓吸引過濾具體可藉由使用布氏漏斗、桐山漏斗等並利用隔膜泵（diaphragm pump）等一面吸引一面過濾的方法來進行。另外，為了降低還原步驟中使用的溶劑的殘存率，可重複進行多次所述操作。As a method of adding the NMP-containing solvent in the water removal step in combination with suction filtration, it is preferred to add a solvent containing NMP to the intermediate dispersion and stir it, followed by vacuum suction filtration. The vacuum suction filtration can be specifically carried out by using a Buchner funnel, a Kiriyama funnel or the like and suctioning one surface by a diaphragm pump or the like. Further, in order to reduce the residual ratio of the solvent used in the reduction step, the above operation may be repeated a plurality of times.

另外，亦較佳為藉由蒸餾將水分去除。進行蒸餾的壓力並無限制，就可效率良好地將水分去除的方面而言，較佳為真空蒸餾。Further, it is also preferred to remove moisture by distillation. The pressure at which distillation is carried out is not limited, and in terms of efficiently removing moisture, vacuum distillation is preferred.

[熱處理步驟] 進而，藉由於還原步驟後的任意階段進行將中間體分散液加熱的步驟（熱處理步驟），可減少中間體分散液中的結合水，因此於用於鋰離子電池的情況下，有石墨烯所未完全保持的水的電解引起的氣體產生而帶來的對電池性能的不良影響減少的傾向。熱處理步驟例如可藉由將中間體分散液投入至加熱攪拌裝置，不使其乾燥地一面加熱一面攪拌來進行。加熱溫度較佳為70℃以上，進而佳為80℃以上。關於石墨烯，有時於高溫條件下羥基等一部分的官能基脫離，因此加熱溫度較佳為150℃以下，進而佳為120℃以下。另外，就效率良好地將水分去除的觀點而言，特佳為同時進行熱處理步驟與強力攪拌步驟、即一面加熱一面藉由高剪切攪拌機進行攪拌處理。[Heat treatment step] Further, by performing the step of heating the intermediate dispersion (heat treatment step) at any stage after the reduction step, the bound water in the intermediate dispersion can be reduced, so that in the case of a lithium ion battery, There is a tendency that the adverse effect on battery performance due to gas generation by electrolysis of water which is not completely retained by graphene tends to decrease. The heat treatment step can be carried out, for example, by putting the intermediate dispersion into a heating and stirring apparatus without stirring the mixture while heating. The heating temperature is preferably 70 ° C or higher, and more preferably 80 ° C or higher. In the graphene, a part of the functional groups such as a hydroxyl group may be desorbed under high temperature conditions. Therefore, the heating temperature is preferably 150 ° C or lower, and more preferably 120 ° C or lower. Further, from the viewpoint of efficiently removing moisture, it is particularly preferable to carry out the heat treatment step and the vigorous stirring step, that is, the stirring treatment by a high shear mixer while heating.

另外，於在水分去除步驟中進行蒸餾的情況下，一面加熱至70℃以上一面進行蒸餾，藉此可同時實施熱處理步驟，可藉由一次處理同時將自由水·吸附水·結合水去除，因此為較佳的態樣。該情況下，特佳為一面加熱至70℃以上一面進行真空蒸餾的手法。具體而言，可列舉使用旋轉蒸發器或帶有真空管線的加熱攪拌機等裝置的手法。Further, when the distillation is carried out in the water removal step, the surface is heated to 70° C. or more and distilled, whereby the heat treatment step can be simultaneously performed, and the free water, the adsorbed water, and the bound water can be simultaneously removed by one treatment. For the better aspect. In this case, it is particularly preferable to carry out vacuum distillation while heating to 70 ° C or higher. Specifically, a method using a device such as a rotary evaporator or a heating mixer with a vacuum line can be cited.

＜石墨烯-電極活性物質複合體粒子＞ 本發明的石墨烯分散液的用途並不受到限定，作為一例，於將石墨烯與鋰離子電池電極活性物質粒子等電極活性物質粒子複合化時可有益地使用。此處，所謂複合化是指維持使石墨烯與電極活性物質粒子的表面接觸的狀態。作為複合化的態樣，可列舉將石墨烯與電極活性物質粒子作為一體而造粒者、或者使石墨烯附著於電極活性物質粒子的表面而成者。<Graphene-electrode active material composite particle> The use of the graphene dispersion liquid of the present invention is not limited, and as an example, it may be advantageous when a combination of graphene and an electrode active material particle such as a lithium ion battery electrode active material particle is used. Use. Here, the term "compositing" means maintaining a state in which graphene is brought into contact with the surface of the electrode active material particles. As a composite aspect, the graphene and the electrode active material particles are integrated as a granule, or graphene is adhered to the surface of the electrode active material particle.

於在石墨烯-電極活性物質複合體粒子的製造中應用的情況下，活性物質可為正極活性物質、負極活性物質的任一種。即，本發明的石墨烯分散液可於正極的製造、亦可於負極的製造中使用。於應用於鋰離子電池電極活性物質粒子的情況下，正極活性物質並無特別限定，可列舉鈷酸鋰（LiCoO2 ）、鎳酸鋰（LiNiO2 ）、尖晶石型錳酸鋰（LiMn2 O4 ）、或以鎳、錳對鈷的一部分進行置換的三元系（LiMnx Niy Co1-x-y O2 ）、尖晶石型錳酸鋰（LiMn2 O4 ）等的鋰與過渡金屬的複合氧化物、磷酸鐵鋰（LiFePO4 ）等的橄欖石系（磷酸系）活性物質、V2 O5 等的金屬氧化物或TiS2 、MoS2 、NbSe2 等的金屬化合物等。作為負極活性物質，並無特別限定，可列舉天然石墨、人造石墨、硬碳等碳系材料、以SiO或SiC、SiOC等為基本構成元素的矽化合物、鈦酸鋰（Li4 Ti5 O12 ）、可與鋰離子進行轉換反應的氧化錳（MnO）或氧化鈷（CoO）等的金屬氧化物等。In the case of application to the production of graphene-electrode active material composite particles, the active material may be either a positive electrode active material or a negative electrode active material. That is, the graphene dispersion liquid of the present invention can be used for the production of a positive electrode or for the production of a negative electrode. When applied to a lithium ion battery electrode active material particle, the positive electrode active material is not particularly limited, and examples thereof include lithium cobaltate (LiCoO 2 ), lithium nickelate (LiNiO 2 ), and spinel lithium manganate (LiMn 2 ). O 4 ) or lithium and transitions such as ternary system (LiMn x Ni y Co 1-xy O 2 ) and spinel lithium manganate (LiMn 2 O 4 ) substituted with a part of cobalt by nickel or manganese An olivine-based (phosphoric acid) active material such as a metal composite oxide, lithium iron phosphate (LiFePO 4 ), a metal oxide such as V 2 O 5 , or a metal compound such as TiS 2 , MoS 2 or NbSe 2 . The negative electrode active material is not particularly limited, and examples thereof include a carbon-based material such as natural graphite, artificial graphite, and hard carbon, and a ruthenium compound or a lithium titanate (Li 4 Ti 5 O 12 ) having SiO, SiC, or SiOC as a basic constituent element. a metal oxide such as manganese oxide (MnO) or cobalt oxide (CoO) which can be converted and reacted with lithium ions.

石墨烯-電極活性物質複合體粒子可藉由將本發明的石墨烯分散液與活性物質粒子加以混合後，利用噴霧乾燥、凍結乾燥等手法進行乾燥來製作。作為將石墨烯分散液與活性物質粒子加以混合的方法，可列舉利用三輥、濕式珠磨機、濕式行星球磨機、均質機、行星式攪拌機、雙軸混煉機等的方法。The graphene-electrode active material composite particles can be produced by mixing the graphene dispersion liquid of the present invention with active material particles, followed by drying by a method such as spray drying or freeze drying. Examples of the method of mixing the graphene dispersion liquid and the active material particles include a three-roller, a wet bead mill, a wet planetary ball mill, a homogenizer, a planetary mixer, and a biaxial kneader.

＜電極糊的製造方法＞ 本發明的石墨烯分散液亦可用於製造鋰離子電池用電極等的製造中所使用的電極糊。即，於視需要添加適量的溶劑後，將電極活性物質、黏合劑及作為導電助劑的本發明的石墨烯分散液混合，藉此可製備電極糊。<Method for Producing Electrode Paste> The graphene dispersion liquid of the present invention can also be used for producing an electrode paste used in the production of an electrode for a lithium ion battery or the like. In other words, an electrode paste can be prepared by mixing an electrode active material, a binder, and a graphene dispersion of the present invention as a conductive auxiliary agent after adding an appropriate amount of a solvent as needed.

作為應用於鋰離子電池的電極糊的製造的情況下的電極活性物質，可使用與所述石墨烯-活性物質複合體粒子的製造方法中所述者相同的活性物質。As the electrode active material used in the production of the electrode paste for a lithium ion battery, the same active material as described in the method for producing the graphene-active material composite particles can be used.

作為黏合劑，並無特別限定，可列舉聚偏二氟乙烯（Polyvinylidenefluoride，PVDF）、聚四氟乙烯（Polytetrafluoroethylene，PTFE）等氟系聚合體、或者苯乙烯丁二烯（Styrene Butadiene，SBR）、天然橡膠等橡膠、羧基甲基纖維素等多糖類、聚醯亞胺前驅物及/或聚醯亞胺樹脂、聚醯胺醯亞胺樹脂、聚醯胺樹脂、聚丙烯酸、聚丙烯酸鈉、丙烯酸系樹脂、聚丙烯腈等。該些可以兩種以上的混合物的形式使用。The binder is not particularly limited, and examples thereof include a fluorine-based polymer such as polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE), or Styrene Butadiene (SBR). Rubber such as natural rubber, polysaccharides such as carboxymethyl cellulose, polyimine precursor and/or polyimine resin, polyamidimide resin, polyamide resin, polyacrylic acid, sodium polyacrylate, acrylic acid Resin, polyacrylonitrile, and the like. These may be used in the form of a mixture of two or more.

導電助劑可僅為本發明的石墨烯分散液中所含的石墨烯，另外亦可進而添加追加的導電助劑。作為追加的導電助劑，並無特別限定，例如可列舉爐黑、科琴黑（Ketjen Black）（註冊商標）、乙炔黑等碳黑類、天然石墨（鱗片狀石墨等）、人造石墨等石墨類、碳纖維及金屬纖維等的導電性纖維類、銅、鎳、鋁及銀等的金屬粉末類等。The conductive auxiliary agent may be only graphene contained in the graphene dispersion liquid of the present invention, and an additional conductive auxiliary agent may be further added. The additional conductive auxiliary agent is not particularly limited, and examples thereof include graphite black, Ketjen Black (registered trademark), carbon black such as acetylene black, natural graphite (flaky graphite), and graphite such as artificial graphite. Conductive fibers such as carbon fibers and metal fibers, metal powders such as copper, nickel, aluminum, and silver.

作為追加使用的溶劑，可列舉NMP、γ-丁內酯、水、二甲基乙醯胺等，最佳為使用作為本發明的石墨烯分散液中所含的溶劑的NMP。 [實施例]Examples of the solvent to be additionally used include NMP, γ-butyrolactone, water, dimethylacetamide, and the like, and NMP which is a solvent contained in the graphene dispersion of the present invention is preferably used. [Examples]

[測定例1：X射線光電子測定] 各樣品的X射線光電子測定是使用庫特拉（Quantera）SXM（PHI公司製造）進行測定。激發X射線是單色鋁（monochromatic Al）Kα1,2射線（1486.6 eV），X射線直徑為200 μm，光電子脫出角度為45°。將基於碳原子的C1s主波峰設為284.3 eV，基於氧原子的O1s波峰屬於533 eV附近的波峰，基於氮原子的N1s波峰屬於402 eV附近的波峰，根據各波峰的面積比求出O/C比及N/C比。[Measurement Example 1: X-ray photoelectron measurement] The X-ray photoelectron measurement of each sample was measured using a Quantera SXM (manufactured by PHI Corporation). The excited X-rays were monochromatic Al Kα1, 2 rays (1486.6 eV), X-ray diameters of 200 μm, and photoelectron extraction angles of 45°. The main peak of C1s based on carbon atoms is set to 284.3 eV, the peak of O1s based on oxygen atoms belongs to the peak near 533 eV, and the peak of N1s based on nitrogen atom belongs to the peak near 402 eV, and O/C is obtained according to the area ratio of each peak. Compared with the N/C ratio.

[測定例2：比表面積的評價] 石墨烯的比表面積測定是使用HM莫德爾（Model）-1210（邁克斯波（Macsorb）公司製造）而進行測定。測定是依據JIS Z8830：2013，以載氣法作為吸附氣體量的測定方法，以一點法進行吸附資料的解析來測定。脫氣條件設為100℃×180分鐘。測定是對重複實施5次如下清洗步驟進行清洗並進而進行凍結乾燥而獲得的石墨烯粉末進行，所述清洗步驟為利用吸引過濾器對下述實施例中製備的還原後的石墨烯水分散液進行過濾後，利用水稀釋至0.5質量%為止而進行吸引過濾。[Measurement Example 2: Evaluation of specific surface area] The specific surface area of graphene was measured by using HM Model-1210 (manufactured by Macsorb). The measurement was carried out in accordance with JIS Z8830:2013, using a carrier gas method as a method for measuring the amount of adsorbed gas, and analyzing the adsorption data by a one-point method. The degassing conditions were set to 100 ° C × 180 minutes. The measurement is performed on the graphene powder obtained by repeatedly performing the following washing step and then performing freeze-drying, which is a reduced graphene aqueous dispersion prepared in the following examples by using a suction filter. After filtration, suction filtration was carried out by diluting with water to 0.5% by mass.

[測定例3：固體成分率（G）] 使石墨烯分散液附著於重量已知的玻璃基板上並測定重量，於溫度調整為120℃的加熱板上加熱1.5小時而使溶劑揮發。根據加熱前的石墨烯分散液的附著量、及由加熱前後的重量差算出的溶劑揮發量來對石墨烯分散液的固體成分率G（質量%）進行測定。將所述操作重複進行3次，並進行平均而求出。[Measurement Example 3: Solid content ratio (G)] The graphene dispersion liquid was adhered to a glass substrate having a known weight, and the weight was measured, and the mixture was heated on a hot plate adjusted to a temperature of 120 ° C for 1.5 hours to volatilize the solvent. The solid content ratio G (% by mass) of the graphene dispersion liquid was measured based on the adhesion amount of the graphene dispersion liquid before heating and the amount of solvent evaporation calculated from the difference in weight before and after heating. The operation was repeated three times and averaged.

[測定例4：吸光度] 各樣品的吸光度是使用U-3010型分光光度計（日立高新技術（Hitachi High-Tech Science）公司製造）而測定。比色皿使用光學長度10 mm的石英製。測定是於事先利用稀釋液所含有比率的混合溶劑進行基線測定的基礎上對如下稀釋液進行，所述稀釋液是於下述實施例製備的石墨烯分散液或石墨烯粉末中以石墨烯重量分率成為0.000013的方式添加NMP，並使用輸出功率為130W、振動頻率為40 kHz的超音波清洗機（ASU-6M，亞速旺（ASONE）公司製造）以高輸出設定進行10分鐘處理而得者。根據所獲得的270 nm的吸光度算出下述式（1）定義的重量吸光係數， 重量吸光係數（cm-1 ）=吸光度/{（0.000013×比色皿的光學長度（cm））} ···（1）。 另外，算出下述式（2）定義的吸光度比， 吸光度比=吸光度（270 nm）/吸光度（600 nm） ···（2）。[Measurement Example 4: Absorbance] The absorbance of each sample was measured using a U-3010 spectrophotometer (manufactured by Hitachi High-Tech Science Co., Ltd.). The cuvette is made of quartz with an optical length of 10 mm. The measurement is performed on the basis of the baseline measurement using a mixed solvent of the ratio contained in the diluent in advance, and the dilution is a graphene weight in the graphene dispersion or the graphene powder prepared in the following examples. NMP was added in such a manner that the fraction was 0.000013, and an ultrasonic cleaning machine (ASU-6M, manufactured by ASONE) having an output of 130 W and a vibration frequency of 40 kHz was used for processing for 10 minutes with a high output setting. By. The weight absorption coefficient defined by the following formula (1) was calculated from the obtained absorbance at 270 nm, and the weight absorption coefficient (cm -1 ) = absorbance / {(0.000013 × optical length (cm) of the cuvette)} ··· (1). Further, the absorbance ratio defined by the following formula (2) was calculated, and the absorbance ratio = absorbance (270 nm) / absorbance (600 nm) · (2).

[測定例5：石墨烯的中間值徑度（D）] 使用NMP將石墨烯分散液或石墨烯粉末稀釋為0.5質量%，將利用使用堀場（HORIBA）公司製造的粒度分佈測定裝置雷射散射粒度分佈分析儀（LASER SCATTERING PARTICLE SIZE DISTRIBUTION ANALYZER）LA-920的雷射繞射/散射式粒度分佈測定法測定的對應於粒度分佈的中央值的粒徑設為中間值徑度（D，μm）。裝置內的溶劑使用與石墨烯分散液的溶劑相同的溶劑，不實施作為測定前處理的超音波施加而進行測定。石墨烯的折射率為1.43。[Measurement Example 5: Intermediate Diameter (D) of Graphene] The graphene dispersion or the graphene powder was diluted to 0.5% by mass using NMP, and laser scattering was performed by using a particle size distribution measuring device manufactured by HORIBA. Particle size distribution analyzer (LASER SCATTERING PARTICLE SIZE DISTRIBUTION ANALYZER) LA-920 Laser diffraction/scattering particle size distribution measurement The particle size corresponding to the median value of the particle size distribution is set to the median diameter (D, μm) . The solvent in the apparatus was the same as the solvent of the graphene dispersion, and the measurement was performed without applying the ultrasonic wave as the pre-measurement treatment. The refractive index of graphene is 1.43.

[測定例6：石墨烯的厚度（T）] 使用NMP將石墨烯分散液或石墨烯粉末稀釋為0.002質量%為止，滴加至雲母基板上並進行乾燥而附著於基板上。利用原子力顯微鏡（迪門肖艾克（Dimension Icon）；布魯克（Bruker）公司製造）對基板上的石墨烯進行觀察，隨機對50個石墨烯的厚度進行測定，將其平均值設為T（nm）。於在一小片中存在厚度不均的情況下，求出面積平均厚度。[Measurement Example 6: Thickness (T) of graphene] The graphene dispersion or graphene powder was diluted to 0.002% by mass with NMP, dropped onto a mica substrate, dried, and adhered to the substrate. The graphene on the substrate was observed by an atomic force microscope (Dimension Icon; manufactured by Bruker), and the thickness of 50 graphene was randomly measured, and the average value was set to T (nm). ). In the case where there is thickness unevenness in a small piece, the area average thickness is obtained.

[測定例7：石墨烯的面方向的大小（S）] 使用NMP溶劑將石墨烯分散液或石墨烯粉末稀釋為0.002質量%，滴加至玻璃基板上並進行乾燥而附著於基板上。利用基恩斯（Keyencec）公司製造的雷射顯微鏡VK-X250觀察基板上的石墨烯，隨機測定50個石墨烯的小片的最長部分的長度（長徑，μm）與最短部分的長度（短徑，μm），並對50個利用（長徑+短徑）/2所求出的數值進行平均而設為石墨烯的面方向的大小（S，μm）。[Measurement Example 7: Size of the graphene in the surface direction (S)] The graphene dispersion or graphene powder was diluted to 0.002% by mass using an NMP solvent, dropped onto a glass substrate, and dried to adhere to the substrate. The graphene on the substrate was observed using a laser microscope VK-X250 manufactured by Keyencec, and the length (long diameter, μm) of the longest portion of the 50 graphene pieces and the length of the shortest portion (short diameter, μm) were randomly determined. The average value obtained by using 50 (long diameter + short diameter)/2 is averaged to the size (S, μm) of the surface direction of graphene.

[測定例8：含水率測定] 石墨烯分散液或石墨烯粉末的含水率測定是使用卡爾費歇爾水分計AQ-2200與水分汽化裝置EV-2010（平沼產業股份有限公司製造），並藉由JIS K0113：2005的8.3項中所示的水分汽化-電量滴定法而測定。藉由於水分汽化裝置中投入石墨烯分散液，並加熱至130℃或250℃而進行測定，獲得含水率W1（質量%）、含水率W2（質量%）的值。[Measurement Example 8: Measurement of water content] The moisture content of the graphene dispersion or graphene powder was measured using a Karl Fischer moisture meter AQ-2200 and a water vaporization apparatus EV-2010 (manufactured by Hiranuma Sangyo Co., Ltd.). It was measured by the moisture vaporization-electricity titration method shown in 8.3 of JIS K0113:2005. The graphene dispersion liquid was charged in the water vaporization apparatus and heated to 130 ° C or 250 ° C to measure the water content W1 (% by mass) and the water content W2 (% by mass).

[測定例9：電池性能評價] 除了各實施例、比較例中特別記載的情況以外，放電容量是以如下方式測定。利用行星式攪拌機將調配有作為石墨烯固體成分的各實施例、比較例中製備的石墨烯分散液或石墨烯粉末1.5質量份、作為電極活性物質的LiNi0.5 Co0.2 Mn0.3 O2 100質量份、作為追加的導電助劑的乙炔黑1.5質量份、作為黏合劑的聚偏二氟乙烯5質量份、作為溶劑的NMP 100質量份者加以混合而獲得電極糊。使用刮刀（300 μm）將所述電極糊塗佈於鋁箔（厚度18 μm），於80℃下乾燥15分鐘後，進行真空乾燥而獲得電極板。[Measurement Example 9: Battery performance evaluation] The discharge capacity was measured in the following manner except for the cases described in the respective examples and comparative examples. 1.5 parts by mass of graphene dispersion or graphene powder prepared in each of the examples and the comparative examples, which are solid components of graphene, and LiNi 0.5 Co 0.2 Mn 0.3 O 2 as an electrode active material, 100 parts by mass, using a planetary mixer 1.5 parts by mass of acetylene black as an additional conductive auxiliary agent, 5 parts by mass of polyvinylidene fluoride as a binder, and 100 parts by mass of NMP as a solvent were mixed to obtain an electrode paste. The electrode paste was applied to an aluminum foil (thickness: 18 μm) using a doctor blade (300 μm), dried at 80 ° C for 15 minutes, and then vacuum dried to obtain an electrode plate.

將所製作的電極板切成直徑15.9 mm並設為正極，將包含石墨98質量份、羧基甲基纖維素鈉1質量份、SBR水分散液1質量份的負極切成直徑16.1 mm而用作異性極。作為切成直徑為17 mm的卡爾格德（Celgard）#2400（卡爾格德公司製造）隔膜，將含有1 M LiPF6 的碳酸伸乙酯：碳酸二乙酯=7：3的溶劑設為電解液，製作2042型紐扣電池。於上限電壓4.2 V、下限電壓3.0 V下按照倍率0.1 C、1 C、5 C的順序各進行3次充放電測定，然後於1 C下進而進行491次、合計500次的充放電測定。對3次倍率1 C、3次倍率5 C、其後的491次倍率1 C（合計500次）的各放電容量進行測定。The produced electrode plate was cut into a diameter of 15.9 mm and set as a positive electrode, and a negative electrode containing 98 parts by mass of graphite, 1 part by mass of sodium carboxymethylcellulose, and 1 part by mass of an aqueous dispersion of SBR was cut into a diameter of 16.1 mm and used as a positive electrode. Heterosexual. As a separator cut into a diameter of 17 mm, Celgard #2400 (manufactured by Calgrade), a solvent containing 1 M LiPF 6 of ethyl carbonate: diethyl carbonate = 7:3 was used for electrolysis. Liquid, making 2042 button battery. The charge/discharge measurement was performed three times in the order of 0.1 C, 1 C, and 5 C at an upper limit voltage of 4.2 V and a lower limit voltage of 3.0 V, and then 491 times and a total of 500 times of charge and discharge measurement were performed at 1 C. The respective discharge capacities of the 3 times magnification 1 C, the 3 times magnification 5 C, and the subsequent 491 times magnification 1 C (total 500 times) were measured.

（合成例1：氧化石墨烯凝膠的製備方法） 將1500網目的天然石墨粉末（上海一帆石墨有限公司製造）作為原料，於冰浴中的10 g的天然石墨粉末中加入220 ml的98%濃硫酸、5 g的硝酸鈉、30 g的高錳酸鉀，進行1小時機械攪拌，將混合液的溫度保持為20℃以下，將該混合液自冰浴中取出，於35℃水浴中進行4小時攪拌反應，其後將加入離子交換水500 ml而獲得的懸浮液於90℃下進而進行15分鐘反應，最後加入600 ml的離子交換水與50 ml的過氧化氫，進行5分鐘反應，而獲得氧化石墨烯分散液，趁熱對其進行過濾，利用稀鹽酸溶液清洗金屬離子，利用離子交換水清洗酸，重複進行清洗直至pH值成為7為止，而製備氧化石墨烯凝膠。所製備的氧化石墨烯的藉由X射線光電子分光法所測定的氧原子相對於碳原子的元素比為0.53。(Synthesis Example 1: Preparation Method of Graphene Oxide Gel) 1500 mesh natural graphite powder (manufactured by Shanghai Yifan Graphite Co., Ltd.) was used as a raw material, and 220 g of 98 g was added to 10 g of natural graphite powder in an ice bath. % concentrated sulfuric acid, 5 g of sodium nitrate, 30 g of potassium permanganate, mechanically stirred for 1 hour, the temperature of the mixture was kept below 20 ° C, and the mixture was taken out from the ice bath in a water bath at 35 ° C The reaction was stirred for 4 hours, and then the suspension obtained by adding 500 ml of ion-exchanged water was further reacted at 90 ° C for 15 minutes, and finally 600 ml of ion-exchanged water and 50 ml of hydrogen peroxide were added for 5 minutes. The graphene oxide dispersion was obtained, filtered while hot, the metal ions were washed with a dilute hydrochloric acid solution, the acid was washed with ion-exchanged water, and the washing was repeated until the pH became 7, to prepare a graphene oxide gel. The element ratio of the oxygen atom to the carbon atom determined by X-ray photoelectron spectroscopy of the produced graphene oxide was 0.53.

[實施例1] 利用離子交換水將合成例1中製備的氧化石墨烯凝膠稀釋為濃度30 mg/ml，利用超音波清洗機進行30分鐘處理，而獲得均勻的氧化石墨烯分散液。[Example 1] The graphene oxide gel prepared in Synthesis Example 1 was diluted to a concentration of 30 mg/ml with ion-exchanged water, and treated with an ultrasonic cleaner for 30 minutes to obtain a uniform graphene oxide dispersion.

將所述氧化石墨烯分散液20 ml與作為表面處理劑的0.3 g的多巴胺鹽酸鹽混合，使用均質分散機2.5型（譜萊密克司公司製造）以轉速3000 rpm進行60分鐘處理（表面處理步驟）。於處理後利用離子交換水將氧化石墨烯分散液稀釋為5 mg/ml，並於稀釋的分散液20 ml中加入0.3 g的二亞硫磺酸鈉，於40℃下進行1小時還原反應（還原步驟）。其後，重複進行5次如下清洗步驟來進行清洗，所述清洗步驟為利用減壓吸引過濾器進行過濾，進而利用離子交換水稀釋至0.5質量%為止而進行吸引過濾。於清洗後利用NMP稀釋至0.5質量%為止（含NMP的溶劑混合步驟），使用菲萊密克司（註冊商標）30-30型（譜萊密克司公司製造）以旋轉速度40 m/s（剪切速度：每秒20000）進行60秒處理（強力攪拌步驟）並吸引過濾。重複進行2次如下步驟（水分去除步驟），而獲得石墨烯NMP分散液，所述步驟為於過濾後利用NMP稀釋至0.5質量%為止，使用均質分散機2.5型（譜萊密克司公司製造）以轉速3000 rpm進行30分鐘處理並吸引過濾。20 ml of the graphene oxide dispersion was mixed with 0.3 g of dopamine hydrochloride as a surface treatment agent, and treated by a homodisperser type 2.5 (manufactured by Specimex Co., Ltd.) at a rotational speed of 3000 rpm for 60 minutes (surface treatment) step). After the treatment, the graphene oxide dispersion was diluted to 5 mg/ml with ion-exchanged water, and 0.3 g of sodium disulfite was added to 20 ml of the diluted dispersion, and the reduction reaction was carried out at 40 ° C for 1 hour. step). Thereafter, the cleaning was carried out by repeating the washing step by suction filtration using a vacuum suction filter and diluting to 0.5% by mass with ion-exchanged water to perform suction filtration. After washing, it was diluted to 0.5% by mass with NMP (solvent mixing step containing NMP), and used at a rotation speed of 40 m/s using a Phillips (registered trademark) type 30-30 (manufactured by Spectrum Microsystems). Cutting speed: 20000 per second) Perform a 60 second treatment (strong stirring step) and draw the filter. The following procedure (moisture removal step) was repeated twice to obtain a graphene NMP dispersion, which was diluted to 0.5% by mass with NMP after filtration, and a homodisperser type 2.5 (manufactured by Specimex Co., Ltd.) was used. The treatment was carried out at 3000 rpm for 30 minutes and suction filtration.

關於所獲得的石墨烯NMP分散液，按照測定例3對固體成分率G進行測定，按照測定例4獲得吸光度、重量吸光係數、吸光度比的值。另外，按照測定例5、測定例6、測定例7對石墨烯的中間值徑度D、石墨烯的厚度T、石墨烯的面方向的大小S、D/S、S/T進行測定，按照測定例8獲得W1、W2、（W2-W1）/G的值。為了進行分析，於利用水將石墨烯NMP分散液稀釋為3倍進行吸引過濾後，進而重複進行2次稀釋、吸引過濾，獲得0.5質量%的石墨烯水分散液，然後進行凍結乾燥而獲得石墨烯粉末。關於所獲得的石墨烯粉末，按照測定例1、測定例2獲得比表面積、（W2-W1）/（G×比表面積）、O/C比、N/C比的值。另外，使用所獲得的石墨烯NMP分散液並按照測定例9進行電池性能評價，而獲得放電容量。將所獲得的結果匯總於表1及表2中。With respect to the obtained graphene NMP dispersion, the solid content ratio G was measured in accordance with Measurement Example 3, and the values of the absorbance, the weight absorption coefficient, and the absorbance ratio were obtained in accordance with Measurement Example 4. Further, according to Measurement Example 5, Measurement Example 6, and Measurement Example 7, the intermediate value diameter D of graphene, the thickness T of graphene, and the size S of the surface direction of graphene, D/S, and S/T were measured. In Measurement Example 8, the values of W1, W2, and (W2-W1)/G were obtained. For the analysis, the graphene NMP dispersion was diluted to 3 times with water to carry out suction filtration, and then the dilution and suction filtration were repeated twice to obtain a 0.5% by mass aqueous graphene dispersion, followed by freeze-drying to obtain graphite. Alkene powder. With respect to the obtained graphene powder, the specific surface area, the value of (W2-W1)/(G* specific surface area), the O/C ratio, and the N/C ratio were obtained according to Measurement Example 1 and Measurement Example 2. Further, using the obtained graphene NMP dispersion and performing battery performance evaluation according to Measurement Example 9, a discharge capacity was obtained. The results obtained are summarized in Tables 1 and 2.

[實施例2] 將強力攪拌步驟中的菲萊密克司的旋轉速度變更為30 m/s（剪切速度：每秒15000），除此以外，與實施例1同樣地製備石墨烯NMP分散液。[Example 2] A graphene NMP dispersion was prepared in the same manner as in Example 1 except that the rotational speed of the Phillips in the vigorous stirring step was changed to 30 m/s (shearing speed: 15,000 per second). .

關於所獲得的石墨烯NMP分散液，按照測定例3對固體成分率G進行測定，按照測定例4對吸光度、重量吸光係數、吸光度比進行測定。另外，按照測定例6、測定例7對石墨烯的厚度T、石墨烯的面方向的大小S進行測定。為了進行分析，於利用水將石墨烯NMP分散液稀釋為3倍進行吸引過濾後，進而重複進行2次稀釋、吸引過濾，獲得0.5質量%的石墨烯水分散液，然後進行凍結乾燥而獲得石墨烯粉末。關於所獲得的石墨烯粉末，按照測定例1、測定例2獲得比表面積、O/C比、N/C比的值。另外，使用所獲得的石墨烯NMP分散液並按照測定例9進行電池性能評價，而獲得放電容量。將所獲得的結果匯總於表1中。With respect to the obtained graphene NMP dispersion, the solid content ratio G was measured in accordance with Measurement Example 3, and the absorbance, the weight absorption coefficient, and the absorbance ratio were measured in accordance with Measurement Example 4. Further, the thickness T of the graphene and the size S of the surface direction of the graphene were measured in Measurement Example 6 and Measurement Example 7. For the analysis, the graphene NMP dispersion was diluted to 3 times with water to carry out suction filtration, and then the dilution and suction filtration were repeated twice to obtain a 0.5% by mass aqueous graphene dispersion, followed by freeze-drying to obtain graphite. Alkene powder. With respect to the obtained graphene powder, the values of the specific surface area, the O/C ratio, and the N/C ratio were obtained in Measurement Example 1 and Measurement Example 2. Further, using the obtained graphene NMP dispersion and performing battery performance evaluation according to Measurement Example 9, a discharge capacity was obtained. The results obtained are summarized in Table 1.

[實施例3] 將強力攪拌步驟中的菲萊密克司的旋轉速度變更為20 m/s（剪切速度：每秒10000），除此以外，與實施例1同樣地製備石墨烯NMP分散液。 與實施例2同樣地進行物性評價、電池性能評價。將所獲得的結果匯總於表1中。[Example 3] A graphene NMP dispersion was prepared in the same manner as in Example 1 except that the rotational speed of the Phillips in the vigorous stirring step was changed to 20 m/s (shearing speed: 10,000 per second). . Physical property evaluation and battery performance evaluation were performed in the same manner as in Example 2. The results obtained are summarized in Table 1.

[實施例4] 將表面處理劑變更為0.3 g的安替比林，除此以外，與實施例1同樣地製備石墨烯NMP分散液。 與實施例2同樣地進行物性評價、電池性能評價。將所獲得的結果匯總於表1中。[Example 4] A graphene NMP dispersion liquid was prepared in the same manner as in Example 1 except that the surface treatment agent was changed to 0.3 g of antipyrine. Physical property evaluation and battery performance evaluation were performed in the same manner as in Example 2. The results obtained are summarized in Table 1.

[實施例5] 將表面處理劑變更為0.3 g的兒茶酚，除此以外，與實施例1同樣地製備石墨烯NMP分散液。 與實施例2同樣地進行物性評價、電池性能評價。將所獲得的結果匯總於表1中。[Example 5] A graphene NMP dispersion liquid was prepared in the same manner as in Example 1 except that the surface treatment agent was changed to 0.3 g of catechol. Physical property evaluation and battery performance evaluation were performed in the same manner as in Example 2. The results obtained are summarized in Table 1.

[實施例6] 並不添加表面處理劑，除此以外，與實施例1同樣地製備石墨烯NMP分散液。 與實施例2同樣地進行物性評價、電池性能評價。將所獲得的結果匯總於表1中。[Example 6] A graphene NMP dispersion liquid was prepared in the same manner as in Example 1 except that the surface treatment agent was not added. Physical property evaluation and battery performance evaluation were performed in the same manner as in Example 2. The results obtained are summarized in Table 1.

[實施例7] 添加表面處理劑，並於利用均質分散機2.5型（譜萊密克司公司製造）進行處理後且於利用離子交換水將氧化石墨烯分散液稀釋為5 mg/ml前，使用超音波裝置UP400S（海樂斯爾（hielscher）公司製造），以輸出功率300 W對氧化石墨烯分散液施加40分鐘超音波（微細化步驟），除此以外，與實施例1同樣地製備石墨烯NMP分散液。 與實施例1同樣地進行物性評價、電池性能評價。將所獲得的結果匯總於表2中。[Example 7] A surface treatment agent was added, and after being treated with a homodisperser type 2.5 (manufactured by Specimol Co., Ltd.) and before the graphene oxide dispersion was diluted to 5 mg/ml with ion-exchanged water, it was used. Graphite was prepared in the same manner as in Example 1 except that the ultrasonic device UP400S (manufactured by Hielscher Co., Ltd.) was subjected to ultrasonic waves for 40 minutes to the graphene oxide dispersion liquid at an output of 300 W (refinement step). Alkene NMP dispersion. Physical property evaluation and battery performance evaluation were performed in the same manner as in Example 1. The results obtained are summarized in Table 2.

[實施例8] 於引用實施例1的實施例7的最後的吸引過濾前，於90℃下對石墨烯NMP分散液進行2小時的加熱還流處理（熱處理），除此以外，全部進行與實施例7同樣的操作，而獲得石墨烯NMP分散液。 與實施例1同樣地進行物性評價、電池性能評價。將所獲得的結果匯總於表2中。[Example 8] Before the final suction filtration of Example 7 of Example 1, the graphene NMP dispersion was heated and reflowed (heat treatment) for 2 hours at 90 ° C, and all were carried out and carried out. The same operation as in Example 7 was carried out to obtain a graphene NMP dispersion. Physical property evaluation and battery performance evaluation were performed in the same manner as in Example 1. The results obtained are summarized in Table 2.

[實施例9] 於進行菲萊密克司處理之前全部進行與實施例7同樣的處理。其後，作為用以去除水分的蒸餾操作，一面於120℃下對石墨烯NMP分散液進行加熱，一面利用隔膜泵進行真空吸引而將水分去除（水分去除步驟）。進而，於在90℃下進行2小時的加熱還流處理（熱處理）後，進行吸引過濾，而獲得石墨烯NMP分散液。 與實施例1同樣地進行物性評價、電池性能評價。將所獲得的結果匯總於表2中。[Example 9] The same treatment as in Example 7 was carried out before the Filomex treatment. Thereafter, as a distillation operation for removing moisture, the graphene NMP dispersion was heated at 120 ° C, and vacuum suction was performed by a diaphragm pump to remove moisture (water removal step). Further, after heating and reflux treatment (heat treatment) at 90 ° C for 2 hours, suction filtration was carried out to obtain a graphene NMP dispersion. Physical property evaluation and battery performance evaluation were performed in the same manner as in Example 1. The results obtained are summarized in Table 2.

[實施例10] 於將與實施例1同樣地獲得的石墨烯NMP分散液與電極活性物質LiNi0.5 Co0. 2 Mn0.3 O2 以固體成分計為3:100的方式混合後，以固體成分率成為10質量%的方式利用NMP進行稀釋並使用菲萊密克司（註冊商標）30-30型（譜萊密克司公司製造）以旋轉速度40 m/s（剪切速度：每秒20000）進行60秒處理。利用噴霧乾燥以入口溫度250℃、出口溫度160℃使處理物乾燥，而獲得石墨烯與電極活性物質LiNi0.5 Co0. 2 Mn0.3 O2 的複合體粒子（石墨烯-電極活性物質複合體粒子）。[Example 10] The graphene NMP dispersion liquid obtained in the same manner as in Example 1 was mixed with the electrode active material LiNi 0.5 Co 0. 2 Mn 0.3 O 2 in a solid content of 3:100, and then solid content was obtained. The rate was 10% by mass, and it was diluted with NMP and used at a rotation speed of 40 m/s (shear speed: 20,000 per second) using the Flemish (registered trademark) Model 30-30 (manufactured by Spectrum Microsystems). 60 seconds processing. The treated material was dried by spray drying at an inlet temperature of 250 ° C and an outlet temperature of 160 ° C to obtain a composite particle of graphene and an electrode active material LiNi 0.5 Co 0.2 2 Mn 0.3 O 2 (graphene-electrode active material composite particle) ).

使用所述複合體粒子作為正極電極活性物質（100質量份），不以單體的形式添加石墨烯分散液，除此以外，與測定例9同樣地進行電池性能評價。 與實施例2同樣地進行物性評價。將所獲得的結果匯總於表1中。The battery performance was evaluated in the same manner as in Measurement Example 9 except that the composite particles were used as the positive electrode active material (100 parts by mass), and the graphene dispersion was not added as a monomer. Physical property evaluation was performed in the same manner as in Example 2. The results obtained are summarized in Table 1.

[比較例1] 於實施例1中，於利用水進行稀釋而吸引過濾的清洗步驟後，利用水稀釋至0.7質量%為止並進行凍結乾燥，而獲得石墨烯粉末。[Comparative Example 1] In the first embodiment, after the washing step of diluting with water to attract the filtration, the mixture was diluted with water to 0.7% by mass and freeze-dried to obtain a graphene powder.

關於所獲得的石墨烯粉末，按照測定例4對吸光度、重量吸光係數、吸光度比進行測定。另外，按照測定例6、測定例7對石墨烯的厚度T、石墨烯的面方向的大小S進行測定，按照測定例1、測定例2獲得比表面積、O/C比、N/C比的值。使用所獲得的石墨烯粉末，按照測定例9進行電池性能評價，而獲得放電容量。將所獲得的結果示於表1中。With respect to the obtained graphene powder, the absorbance, the weight absorption coefficient, and the absorbance ratio were measured in accordance with Measurement Example 4. In addition, in the measurement example 6 and the measurement example 7, the thickness T of the graphene and the size S of the surface direction of the graphene were measured, and the specific surface area, the O/C ratio, and the N/C ratio were obtained according to the measurement example 1 and the measurement example 2. value. Using the obtained graphene powder, battery performance evaluation was carried out in accordance with Measurement Example 9, and a discharge capacity was obtained. The results obtained are shown in Table 1.

[比較例2] 作為相當於強力攪拌步驟的步驟，使用剪切力比菲萊密克司弱的均質分散機2.5型（譜萊密克司公司製造）來代替菲萊密克司，以轉速3000 rpm進行30分鐘處理，除此以外，與實施例1同樣地製備石墨烯NMP分散液。此時，可計算出均質分散機的旋轉刀片的直徑為30 mm，周速為4.7 m/s。攪拌時使用的容器的內徑為50 mm，壁面與旋轉刀片的距離為10 mm。可計算出剪切速度為每秒470。 與實施例2同樣地進行物性評價、電池性能評價。將所獲得的結果匯總於表1中。[Comparative Example 2] As a step corresponding to the intensive stirring step, a homogeneous disperser type 2.5 (manufactured by Spectrum Remex) having a shear force weaker than that of Flemish was used instead of the Flemish, at a rotation speed of 3000 rpm. A graphene NMP dispersion liquid was prepared in the same manner as in Example 1 except that the treatment was carried out for 30 minutes. At this time, it can be calculated that the rotary insert of the homogenizer has a diameter of 30 mm and a peripheral speed of 4.7 m/s. The inner diameter of the container used for agitation is 50 mm and the distance between the wall and the rotating blade is 10 mm. The shear rate can be calculated to be 470 per second. Physical property evaluation and battery performance evaluation were performed in the same manner as in Example 2. The results obtained are summarized in Table 1.

[比較例3] 將水分去除步驟中的吸引過濾變更為離心沈降，除此以外，與實施例1同樣地製備石墨烯NMP分散液。 與實施例2同樣地進行物性評價、電池性能評價。將所獲得的結果匯總於表1中。[Comparative Example 3] A graphene NMP dispersion liquid was prepared in the same manner as in Example 1 except that the suction filtration in the water removal step was changed to centrifugal sedimentation. Physical property evaluation and battery performance evaluation were performed in the same manner as in Example 2. The results obtained are summarized in Table 1.

[比較例4] 以比較例1中所獲得的石墨烯粉末成為0.5質量%的方式添加NMP，並利用菲萊密克司（註冊商標）30-30型（譜萊密克司公司製造）以旋轉速度40 m/s（剪切速度：每秒20000）進行60秒處理，而獲得石墨烯NMP分散液。 與實施例2同樣地進行物性評價、電池性能評價。將所獲得的結果匯總於表1中。[Comparative Example 4] NMP was added in such a manner that the graphene powder obtained in Comparative Example 1 was 0.5% by mass, and a rotation speed was used by using Freimex (registered trademark) Model 30-30 (manufactured by Spectrum Microtek) 40 m/s (shear speed: 20,000 per second) was processed for 60 seconds to obtain a graphene NMP dispersion. Physical property evaluation and battery performance evaluation were performed in the same manner as in Example 2. The results obtained are summarized in Table 1.

所述實施例中，亦對實施例1、實施例7、實施例8、實施例9的石墨烯的中間值徑度D、D/S、S/T、W1、W2、（W2-W1）/G、（W2-W1）/（G×比表面積）進行了測定，故而另外將結果匯總於表2中。In the above embodiments, the intermediate values D, D/S, S/T, W1, W2, (W2-W1) of the graphenes of Example 1, Example 7, Example 8, and Example 9 are also also applied. /G, (W2-W1)/(G* specific surface area) were measured, and the results are summarized in Table 2.

[表1] [Table 1]

[表2] [Table 2]

無no

無no

無no

Claims (15)

一種石墨烯分散液，其為石墨烯分散於含有50質量%以上的N-甲基吡咯啶酮的溶劑中而成的分散液，且利用N-甲基吡咯啶酮將石墨烯重量分率調整為0.000013而得的稀釋液、波長270 nm下的使用下述式（1）算出的重量吸光係數為25000 cm-1 以上且200000 cm-1 以下， 重量吸光係數（cm-1 ）=吸光度/{（0.000013×比色皿的光學長度（cm））} ···（1）。A graphene dispersion liquid in which a graphene is dispersed in a solvent containing 50% by mass or more of N-methylpyrrolidone, and the graphene weight fraction is adjusted by using N-methylpyrrolidone The weight absorption coefficient calculated by the following formula (1) at a dilution of 0.000013 and a wavelength of 270 nm is 25000 cm -1 or more and 200,000 cm -1 or less, and the weight absorption coefficient (cm -1 ) = absorbance / { (0.000013 × optical length (cm) of cuvette)} · (1). 如申請專利範圍第1項所述的石墨烯分散液，其中所述稀釋液的使用下述式（2）而算出的吸光度比為1.70以上且4.00以下， 吸光度比=吸光度（270 nm）/吸光度（600 nm） ···（2）。The graphene dispersion liquid according to the first aspect of the invention, wherein the absorbance ratio calculated by the following formula (2) is 1.70 or more and 4.00 or less, and the absorbance ratio = absorbance (270 nm) / absorbance (600 nm) ···(2). 如申請專利範圍第1項或第2項所述的石墨烯分散液，其中所述石墨烯的藉由X射線光電子分光法所測定的氧相對於碳的元素比（O/C比）為0.05以上且0.40以下。The graphene dispersion according to claim 1 or 2, wherein an elemental ratio (O/C ratio) of oxygen to carbon measured by X-ray photoelectron spectroscopy is 0.05. Above and below 0.40. 如申請專利範圍第1項至第3項中任一項所述的石墨烯分散液，其含有具有酸性基的表面處理劑。The graphene dispersion according to any one of claims 1 to 3, which contains a surface treatment agent having an acidic group. 如申請專利範圍第1項至第4項中任一項所述的石墨烯分散液，其中所述石墨烯的藉由X射線光電子分光法所測定的氮相對於碳的元素比（N/C比）為0.005以上且0.030以下。The graphene dispersion according to any one of claims 1 to 4, wherein an element ratio of nitrogen to carbon measured by X-ray photoelectron spectroscopy of the graphene (N/C) The ratio is 0.005 or more and 0.030 or less. 如申請專利範圍第1項至第5項中任一項所述的石墨烯分散液，其中所述石墨烯的藉由布厄特測定法所測定的比表面積為80 m2 /g以上且250 m2 /g以下。The graphene dispersion according to any one of claims 1 to 5, wherein the graphene has a specific surface area of 80 m 2 /g or more and 250 m as determined by a Bouert assay. 2 / g or less. 如申請專利範圍第1項至第6項中任一項所述的石墨烯分散液，其中固體成分率為0.3質量%以上且40質量%以下。The graphene dispersion liquid according to any one of claims 1 to 6, wherein the solid content ratio is 0.3% by mass or more and 40% by mass or less. 如申請專利範圍第1項至第7項中任一項所述的石墨烯分散液，其中於將藉由雷射繞射/散射式粒度分佈測定法所測定的石墨烯的中間值徑度設為D（μm）且將藉由利用雷射顯微鏡觀察到的石墨烯的最長徑度與最短徑度的相加平均而求出的石墨烯的面方向的大小的平均值設為S（μm）時，同時滿足下述式（3）及式（4）， 0.5 μm≦S≦15 μm ···（3） 1.0≦D/S≦3.0 ···（4）。The graphene dispersion according to any one of claims 1 to 7, wherein the intermediate value of the graphene measured by the laser diffraction/scattering particle size distribution measurement is set. The average value of the surface direction of the graphene obtained by the addition average of the longest diameter and the shortest diameter of the graphene observed by a laser microscope is D (μm), and is S (μm). At the same time, the following formulas (3) and (4) are satisfied, 0.5 μm ≦S ≦ 15 μm · (3) 1.0 ≦ D / S ≦ 3.0 · (4). 如申請專利範圍第1項至第8項中任一項所述的石墨烯分散液，其中於將利用卡爾費歇爾法測定的130℃下的含水率設為W1（質量%）、250℃下的含水率設為W2（質量%）且將石墨烯的固體成分率設為G（質量%）時，（W2-W1）/G的值為0.005以上且0.05以下。The graphene dispersion according to any one of claims 1 to 8, wherein the water content at 130 ° C measured by the Karl Fischer method is set to W1 (% by mass), 250 ° C. When the lower water content is W2 (% by mass) and the solid content ratio of graphene is G (% by mass), the value of (W2-W1)/G is 0.005 or more and 0.05 or less. 一種石墨烯-電極活性物質複合體粒子的製造方法，其包括在將如申請專利範圍第1項至第9項中任一項所述的石墨烯分散液與電極活性物質粒子混合後加以乾燥的操作。A method for producing a graphene-electrode active material composite particle, which comprises mixing a graphene dispersion liquid according to any one of claims 1 to 9 with an electrode active material particle, and drying the same operating. 一種電極糊的製造方法，其包括將電極活性物質、黏合劑及如申請專利範圍第1項至第9項中任一項所述的石墨烯分散液加以混合的操作。A method of producing an electrode paste, comprising the step of mixing an electrode active material, a binder, and a graphene dispersion according to any one of claims 1 to 9. 一種石墨烯分散液的製造方法，其包括： 還原步驟，包括對含有水的分散媒中所分散的氧化石墨烯進行還原； N-甲基吡咯啶酮混合步驟，包括將還原步驟中所獲得的中間體分散液與含有50質量%以上的N-甲基吡咯啶酮的溶劑（含有N-甲基吡咯啶酮的溶劑）加以混合； 強力攪拌步驟，包括以剪切速度為每秒5000～每秒50000對N-甲基吡咯啶酮混合步驟中所獲得的中間體分散液進行攪拌； 水分去除步驟，包括藉由將含有N-甲基吡咯啶酮的溶劑添加與吸引過濾加以組合的手法或者蒸餾而自中間體分散液中去除至少一部分水分。A method for producing a graphene dispersion, comprising: a reduction step comprising: reducing a graphene oxide dispersed in a dispersion medium containing water; and a N-methylpyrrolidone mixing step comprising obtaining the obtained in the reduction step The intermediate dispersion is mixed with a solvent (solvent containing N-methylpyrrolidone) containing 50% by mass or more of N-methylpyrrolidone; a vigorous stirring step including a shear rate of 5000 to 2,000 per second. 1500 seconds of the intermediate dispersion obtained in the N-methylpyrrolidone mixing step; a moisture removal step comprising a combination of adding a solvent containing N-methylpyrrolidone and suction filtration or At least a portion of the water is removed from the intermediate dispersion by distillation. 如申請專利範圍第12項所述的石墨烯分散液的製造方法，其中於所述還原步驟的前後或所述還原步驟的進行中，進而包括 將中間體分散液中所含有的氧化石墨烯或石墨烯微細化的微細化步驟。The method for producing a graphene dispersion according to claim 12, wherein before or after the reducing step or during the reducing step, further comprising graphene oxide contained in the intermediate dispersion or A micronization step of refining graphene. 如申請專利範圍第12項或第13項所述的石墨烯分散液的製造方法，其中於還原步驟後的任意階段，進而包括 將中間體分散液加熱的熱處理步驟。The method for producing a graphene dispersion according to claim 12, wherein the heat treatment step of heating the intermediate dispersion is further included at any stage after the reduction step. 如申請專利範圍第12項至第14項中任一項所述的石墨烯分散液的製造方法，其中於所述還原步驟的前後或所述還原步驟的進行中，進而包括 將中間外分散液與具有酸性基的表面處理劑加以混合的表面處理步驟。The method for producing a graphene dispersion according to any one of claims 12 to 14, wherein the intermediate dispersion is further included before or after the reducing step or during the reducing step A surface treatment step of mixing with a surface treatment agent having an acidic group.
TW105129665A 2015-09-18 2016-09-13 Graphene dispersion liquid and manufacturing method thereof, manufacturing method of graphene-electrode active material composite particles, and manufacturing method of electrode paste TWI694054B (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2015184813 2015-09-18
JP2015-184813 2015-09-18

Publications (2)

Publication Number Publication Date
TW201711959A true TW201711959A (en) 2017-04-01
TWI694054B TWI694054B (en) 2020-05-21

Family

ID=58289187

Family Applications (1)

Application Number Title Priority Date Filing Date
TW105129665A TWI694054B (en) 2015-09-18 2016-09-13 Graphene dispersion liquid and manufacturing method thereof, manufacturing method of graphene-electrode active material composite particles, and manufacturing method of electrode paste

Country Status (8)

Country Link
US (1) US10636586B2 (en)
EP (1) EP3425653A4 (en)
JP (1) JP6152924B1 (en)
KR (1) KR101909424B1 (en)
CN (1) CN108028142B (en)
CA (1) CA2998724C (en)
TW (1) TWI694054B (en)
WO (1) WO2017047521A1 (en)

Families Citing this family (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP6152923B1 (en) * 2015-09-18 2017-06-28 東レ株式会社 Graphene / organic solvent dispersion, method for producing the same, and method for producing an electrode for a lithium ion battery
US10654721B2 (en) 2015-09-18 2020-05-19 Toray Industries, Inc. Graphene dispersion, process for producing same, process for producing particles of graphene/active material composite, and process for producing electrode paste
KR102421959B1 (en) * 2017-03-13 2022-07-18 도레이 카부시키가이샤 Electrode for secondary battery
EP3852168A4 (en) * 2018-09-10 2022-07-27 Toray Industries, Inc. Electrode for secondary battery and secondary battery
WO2020090704A1 (en) 2018-10-31 2020-05-07 東レ株式会社 Graphene dispersion, method for producing same, and electrode for secondary battery
TW202037681A (en) * 2018-11-29 2020-10-16 大陸商東麗先端材料研究開發（中國）有限公司 Graphene anti-corrosion coating with graphene dispersion in the coating is improved and the compactness of the coating is enhanced
CN109553094A (en) * 2019-01-03 2019-04-02 深圳天元羲王材料科技有限公司 A kind of grapheme platelet liquid phase ultrasonic dispersing method
WO2020158887A1 (en) * 2019-02-01 2020-08-06 日亜化学工業株式会社 Method for manufacturing electrode active material for non-aqueous secondary cell
CN110518241B (en) * 2019-08-30 2022-02-18 江西安驰新能源科技有限公司 Efficient dispersion process of graphite negative electrode material
CN111551523A (en) * 2020-05-19 2020-08-18 安徽科达新材料有限公司 Method for rapidly evaluating dispersion performance of positive and negative electrode slurry of battery
CN111785965B (en) * 2020-05-22 2024-02-13 浙江兴海能源科技有限公司 Nanometer graphene material dispersing process
FR3111348B1 (en) * 2020-06-12 2022-07-01 Arkema France Composition for battery electrodes
CN112908956A (en) * 2021-01-29 2021-06-04 南京信息工程大学 Metal oxide/graphene composite fluid and preparation method and application thereof
CN113539697A (en) * 2021-05-28 2021-10-22 武汉工程大学 Reduced graphene oxide/conductive polymer composite gel and preparation method thereof
JP7098076B1 (en) * 2021-10-04 2022-07-08 大日精化工業株式会社 Carbon material dispersion and its use
WO2023059149A1 (en) * 2021-10-07 2023-04-13 주식회사 엘지에너지솔루션 Anode pre-dispersion solution, anode composition comprising same, anode for lithium secondary battery comprising anode composition, lithium secondary battery comprising anode, and method for manufacturing anode composition
CN113881185B (en) * 2021-11-17 2023-04-11 航天特种材料及工艺技术研究所 Graphene modified phenolic resin, preparation method thereof and application thereof in preparation of composite material
CN114345411B (en) * 2022-01-18 2023-12-05 南阳理工学院 Composite material and preparation method and application thereof
CN114479576A (en) * 2022-02-10 2022-05-13 浙江华普环保材料有限公司 Formaldehyde-resistant color steel plate and preparation process thereof
CN114410137A (en) * 2022-03-16 2022-04-29 厦门特聚科技有限公司 Graphene dispersion liquid for solid capacitor and preparation method thereof
CN114956065B (en) * 2022-05-30 2023-09-26 广东墨睿科技有限公司 Amino modified graphene, preparation method thereof, amino modified graphene coating and application

Family Cites Families (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7658901B2 (en) 2005-10-14 2010-02-09 The Trustees Of Princeton University Thermally exfoliated graphite oxide
KR101071224B1 (en) 2009-05-11 2011-10-10 울산대학교 산학협력단 Methods for fabricating the thin film graphene
CN103466602A (en) 2012-06-06 2013-12-25 东丽先端材料研究开发（中国）有限公司 Preparation method of graphene powder, and application of graphene powder in lithium ion battery
JP5933374B2 (en) * 2012-07-03 2016-06-08 ハリマ化成株式会社 Method for producing thin-layer graphite or thin-layer graphite compound
CN103682358A (en) * 2012-09-24 2014-03-26 东丽先端材料研究开发（中国）有限公司 High-dispersity graphene composition and preparation method thereof as well as electrode applied to lithium ion secondary battery
CN103011138B (en) * 2012-11-09 2014-10-22 中国科学院宁波材料技术与工程研究所 Graphene with composite pore structure, preparation method thereof and application in super capacitor
CN103112848B (en) * 2013-03-08 2015-01-07 厦门大学 Method for preparing graphene
GB201304770D0 (en) 2013-03-15 2013-05-01 Provost Fellows Foundation Scholars And The Other Members Of Board Of A scalable process for producing exfoliated defect-free, non-oxidised 2-dimens ional materials in large quantities
JP6304988B2 (en) 2013-09-20 2018-04-04 大阪瓦斯株式会社 Method for producing graphene sheet organic dispersion, and graphene sheet organic dispersion and heat dissipation graphene sheet structure obtained thereby
KR101652921B1 (en) 2013-12-27 2016-08-31 주식회사 엘지화학 Conducting material composition, slurry composition for forming electrode of lithium rechargeable battery and lithium rechargeable battery using the same
TW201531499A (en) * 2014-02-13 2015-08-16 Tosoh Corp Hydrophilic polymer, manufacturing method of the same, and application of hydrophilic polymer
CN104609413B (en) * 2015-02-11 2016-08-24 合肥微晶材料科技有限公司 A kind of tonne of class mechanical stripping device producing Graphene and production method thereof
CN104677846A (en) * 2015-02-28 2015-06-03 济宁利特纳米技术有限责任公司 Quantitative analysis method for graphene dispersion liquid
CN104772064B (en) * 2015-03-31 2017-01-18 山东玉皇新能源科技有限公司 Method for preparing grapheme dispersion liquid
US10654721B2 (en) * 2015-09-18 2020-05-19 Toray Industries, Inc. Graphene dispersion, process for producing same, process for producing particles of graphene/active material composite, and process for producing electrode paste
JP6152923B1 (en) * 2015-09-18 2017-06-28 東レ株式会社 Graphene / organic solvent dispersion, method for producing the same, and method for producing an electrode for a lithium ion battery

Also Published As

Publication number Publication date
TWI694054B (en) 2020-05-21
US10636586B2 (en) 2020-04-28
JP6152924B1 (en) 2017-06-28
CA2998724C (en) 2022-03-22
WO2017047521A1 (en) 2017-03-23
EP3425653A1 (en) 2019-01-09
KR20180044888A (en) 2018-05-03
JPWO2017047521A1 (en) 2017-09-21
CN108028142A (en) 2018-05-11
KR101909424B1 (en) 2018-10-17
US20180261402A1 (en) 2018-09-13
CA2998724A1 (en) 2017-03-23
CN108028142B (en) 2019-02-05
EP3425653A4 (en) 2019-11-06

Similar Documents

Publication Publication Date Title
JP6152924B1 (en) Graphene dispersion and method for producing the same, method for producing graphene-active material composite particles, and method for producing electrode paste
TWI694055B (en) Graphene dispersion liquid and manufacturing method thereof, manufacturing method of graphene-electrode active material composite particles, and manufacturing method of electrode paste
JP6152923B1 (en) Graphene / organic solvent dispersion, method for producing the same, and method for producing an electrode for a lithium ion battery
TWI705600B (en) Positive electrode for lithium ion secondary battery, graphene-positive electrode active material composite particles and their production method, and positive electrode paste for lithium ion secondary battery
KR102275042B1 (en) Graphene dispersion, method for preparing electrode paste, and method for preparing electrode
KR20180120181A (en) Surface treated graphene, surface treated graphene / organic solvent dispersion, surface treated graphene-electrode active material composite particles and electrode paste
KR102320435B1 (en) Graphene dispersion, method for preparing same, and electrode for secondary battery
JP6863099B2 (en) Graphene / Organic Solvent Dispersion, Graphene-Active Material Complex Particle Production Method and Electrode Paste Production Method
KR20220101621A (en) Graphene Dispersion and Positive Electrode Paste
WO2021095651A1 (en) Graphene dispersion, positive electrode paste, and lithium ion battery positive electrode